diff --git a/crates/fuzz/tests/test.rs b/crates/fuzz/tests/test.rs
index b6628072..1a9c2ec7 100644
--- a/crates/fuzz/tests/test.rs
+++ b/crates/fuzz/tests/test.rs
@@ -9572,6 +9572,270 @@ fn tree_none() {
     )
 }
 
+#[test]
+fn checkout_text_err() {
+    test_multi_sites(
+        5,
+        vec![FuzzTarget::All],
+        &mut [
+            Handle {
+                site: 25,
+                target: 25,
+                container: 193,
+                action: Generic(GenericAction {
+                    value: I32(1644825),
+                    bool: false,
+                    key: 393216,
+                    pos: 27487790694400,
+                    length: 1808504320951976800,
+                    prop: 18446744073709551385,
+                }),
+            },
+            SyncAll,
+            Handle {
+                site: 25,
+                target: 25,
+                container: 25,
+                action: Generic(GenericAction {
+                    value: Container(Unknown(255)),
+                    bool: true,
+                    key: 436207615,
+                    pos: 1808504320951916825,
+                    length: 16131858542891077913,
+                    prop: 18437701552104792031,
+                }),
+            },
+            SyncAll,
+            Handle {
+                site: 25,
+                target: 34,
+                container: 25,
+                action: Generic(GenericAction {
+                    value: Container(Unknown(255)),
+                    bool: true,
+                    key: 4294967295,
+                    pos: 18446744073709551615,
+                    length: 18446744073709551615,
+                    prop: 18381750949675392991,
+                }),
+            },
+            SyncAll,
+            Handle {
+                site: 25,
+                target: 25,
+                container: 25,
+                action: Generic(GenericAction {
+                    value: I32(-538976367),
+                    bool: true,
+                    key: 685760479,
+                    pos: 16131858456979185696,
+                    length: 1811037595742312729,
+                    prop: 1849036717598251289,
+                }),
+            },
+            Handle {
+                site: 0,
+                target: 0,
+                container: 0,
+                action: Generic(GenericAction {
+                    value: I32(421068800),
+                    bool: true,
+                    key: 432014617,
+                    pos: 18446744073694419225,
+                    length: 18446744073709551615,
+                    prop: 16131858542891098079,
+                }),
+            },
+            SyncAll,
+            Handle {
+                site: 25,
+                target: 25,
+                container: 255,
+                action: Generic(GenericAction {
+                    value: Container(Text),
+                    bool: true,
+                    key: 421075225,
+                    pos: 16131858204548733209,
+                    length: 2314885568395206623,
+                    prop: 1808505174690352095,
+                }),
+            },
+            Handle {
+                site: 25,
+                target: 25,
+                container: 25,
+                action: Generic(GenericAction {
+                    value: Container(Text),
+                    bool: true,
+                    key: 25,
+                    pos: 1808476725365964800,
+                    length: 11031876360607176985,
+                    prop: 18446744073709486086,
+                }),
+            },
+            SyncAll,
+            Handle {
+                site: 33,
+                target: 33,
+                container: 255,
+                action: Generic(GenericAction {
+                    value: Container(Unknown(255)),
+                    bool: true,
+                    key: 553582865,
+                    pos: 18446744073709551615,
+                    length: 18446744073709551615,
+                    prop: 18446744073709551615,
+                }),
+            },
+            Handle {
+                site: 25,
+                target: 25,
+                container: 25,
+                action: Generic(GenericAction {
+                    value: Container(Unknown(25)),
+                    bool: true,
+                    key: 421075225,
+                    pos: 16131858204548733209,
+                    length: 2314885568395206623,
+                    prop: 1808505174690352095,
+                }),
+            },
+            Handle {
+                site: 25,
+                target: 25,
+                container: 25,
+                action: Generic(GenericAction {
+                    value: Container(Text),
+                    bool: true,
+                    key: 25,
+                    pos: 1808476725365964800,
+                    length: 1808505037875966233,
+                    prop: 18446744073709551385,
+                }),
+            },
+            SyncAll,
+            Handle {
+                site: 25,
+                target: 25,
+                container: 25,
+                action: Generic(GenericAction {
+                    value: Container(Unknown(223)),
+                    bool: true,
+                    key: 538976296,
+                    pos: 1808505174690352095,
+                    length: 1808504321102911769,
+                    prop: 1808504323367835929,
+                }),
+            },
+            Handle {
+                site: 0,
+                target: 0,
+                container: 0,
+                action: Generic(GenericAction {
+                    value: I32(85530905),
+                    bool: false,
+                    key: 421075225,
+                    pos: 18446744073709551615,
+                    length: 16131858680869027839,
+                    prop: 18437701552104792031,
+                }),
+            },
+            SyncAll,
+            Handle {
+                site: 0,
+                target: 0,
+                container: 0,
+                action: Generic(GenericAction {
+                    value: I32(421117957),
+                    bool: true,
+                    key: 4294967065,
+                    pos: 18446744073709551615,
+                    length: 16131858542891106303,
+                    prop: 18446744073170575327,
+                }),
+            },
+            SyncAll,
+            Undo {
+                site: 115,
+                op_len: 1936946035,
+            },
+            Handle {
+                site: 25,
+                target: 255,
+                container: 255,
+                action: Generic(GenericAction {
+                    value: Container(Text),
+                    bool: true,
+                    key: 421075225,
+                    pos: 16131858541569448217,
+                    length: 16077885992209473503,
+                    prop: 1808504324286832587,
+                }),
+            },
+            Handle {
+                site: 25,
+                target: 25,
+                container: 25,
+                action: Generic(GenericAction {
+                    value: I32(421075225),
+                    bool: true,
+                    key: 0,
+                    pos: 1808504213156659200,
+                    length: 18417779746705245465,
+                    prop: 18446744073709551615,
+                }),
+            },
+            SyncAll,
+            Handle {
+                site: 255,
+                target: 255,
+                container: 255,
+                action: Generic(GenericAction {
+                    value: Container(Text),
+                    bool: true,
+                    key: 421075225,
+                    pos: 16131858542885935385,
+                    length: 14690495831856439263,
+                    prop: 1808504320964943839,
+                }),
+            },
+            SyncAll,
+            Handle {
+                site: 25,
+                target: 34,
+                container: 25,
+                action: Generic(GenericAction {
+                    value: Container(Unknown(255)),
+                    bool: true,
+                    key: 4294967295,
+                    pos: 18446744073709551615,
+                    length: 18446744073709551615,
+                    prop: 18381750949675392991,
+                }),
+            },
+            SyncAll,
+            Undo {
+                site: 115,
+                op_len: 1936946035,
+            },
+            SyncAll,
+            Handle {
+                site: 0,
+                target: 0,
+                container: 0,
+                action: Generic(GenericAction {
+                    value: I32(85530905),
+                    bool: false,
+                    key: 2568558873,
+                    pos: 18446744073709551615,
+                    length: 16131858542885935615,
+                    prop: 16131858542891098079,
+                }),
+            },
+        ],
+    )
+}
+
 #[test]
 fn minify() {
     minify_error(
diff --git a/crates/loro-internal/src/container/richtext/tracker.rs b/crates/loro-internal/src/container/richtext/tracker.rs
index ceb64e96..d23c493e 100644
--- a/crates/loro-internal/src/container/richtext/tracker.rs
+++ b/crates/loro-internal/src/container/richtext/tracker.rs
@@ -156,7 +156,7 @@ impl Tracker {
     pub(crate) fn delete(
         &mut self,
         mut op_id: ID,
-        target_start_id: ID,
+        mut target_start_id: ID,
         pos: usize,
         mut len: usize,
         reverse: bool,
@@ -165,6 +165,7 @@ impl Tracker {
             // the op is partially included, need to slice the op
             let start = (applied_counter_end - op_id.counter) as usize;
             op_id.counter = applied_counter_end;
+            target_start_id = target_start_id.inc(start as i32);
             len -= start;
             // If reverse, don't need to change the pos, because it's deleting backwards.
             // If not reverse, we don't need to change the pos either, because the `start` chars after it are already deleted
diff --git a/crates/loro-internal/src/container/richtext/tracker/crdt_rope.rs b/crates/loro-internal/src/container/richtext/tracker/crdt_rope.rs
index a6409ffe..6c3c901c 100644
--- a/crates/loro-internal/src/container/richtext/tracker/crdt_rope.rs
+++ b/crates/loro-internal/src/container/richtext/tracker/crdt_rope.rs
@@ -246,6 +246,7 @@ impl CrdtRope {
         }
 
         if reversed && len > 1 {
+            // TODO: PERF: optimize this
             let mut ans = SmallVec::with_capacity(len);
             for i in (0..len).rev() {
                 let a = self.delete(
diff --git a/crates/loro-internal/src/diff_calc.rs b/crates/loro-internal/src/diff_calc.rs
index f7917b20..e232d00d 100644
--- a/crates/loro-internal/src/diff_calc.rs
+++ b/crates/loro-internal/src/diff_calc.rs
@@ -15,7 +15,7 @@ use loro_common::{
 };
 use loro_delta::DeltaRope;
 use smallvec::SmallVec;
-use tracing::{info, instrument};
+use tracing::{info_span, instrument};
 
 use crate::{
     change::Lamport,
@@ -333,27 +333,30 @@ impl DiffCalculator {
                 let id = oplog.arena.idx_to_id(container_idx).unwrap();
                 let bring_back = new_containers.remove(&id);
 
-                let (diff, diff_mode) = calc.calculate_diff(oplog, before, after, |c| {
-                    new_containers.insert(c.clone());
-                    container_id_to_depth.insert(c.clone(), depth.and_then(|d| d.checked_add(1)));
-                    oplog.arena.register_container(c);
+                info_span!("CalcDiff", ?id).in_scope(|| {
+                    let (diff, diff_mode) = calc.calculate_diff(oplog, before, after, |c| {
+                        new_containers.insert(c.clone());
+                        container_id_to_depth
+                            .insert(c.clone(), depth.and_then(|d| d.checked_add(1)));
+                        oplog.arena.register_container(c);
+                    });
+                    calc.finish_this_round();
+                    if !diff.is_empty() || bring_back {
+                        ans.insert(
+                            container_idx,
+                            (
+                                *depth,
+                                InternalContainerDiff {
+                                    idx: container_idx,
+                                    bring_back,
+                                    is_container_deleted: false,
+                                    diff: diff.into(),
+                                    diff_mode,
+                                },
+                            ),
+                        );
+                    }
                 });
-                calc.finish_this_round();
-                if !diff.is_empty() || bring_back {
-                    ans.insert(
-                        container_idx,
-                        (
-                            *depth,
-                            InternalContainerDiff {
-                                idx: container_idx,
-                                bring_back,
-                                is_container_deleted: false,
-                                diff: diff.into(),
-                                diff_mode,
-                            },
-                        ),
-                    );
-                }
             }
         }