epoch `fetch_update` not working as expected about crossbeam HOT 2 CLOSED

error: Undefined Behavior: Data race detected between (1) Write on thread `<unnamed>` and (2) Write on thread `<unnamed>` at alloc1050. (2) just happened here
   --> /playground/.cargo/registry/src/index.crates.io-6f17d22bba15001f/crossbeam-epoch-0.9.15/src/atomic.rs:208:9
    |
208 |         &mut *(ptr as *mut T)
    |         ^^^^^^^^^^^^^^^^^^^^^ Data race detected between (1) Write on thread `<unnamed>` and (2) Write on thread `<unnamed>` at alloc1050. (2) just happened here
    |
help: and (1) occurred earlier here
   --> src/main.rs:20:21
    |
20  |                     new_obj.count += 1;
    |                     ^^^^^^^^^^^^^
    = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
    = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
    = note: BACKTRACE (of the first span):
    = note: inside `<Obj as crossbeam_epoch::Pointable>::deref_mut::<'_>` at /playground/.cargo/registry/src/index.crates.io-6f17d22bba15001f/crossbeam-epoch-0.9.15/src/atomic.rs:208:9: 208:30
    = note: inside `<crossbeam_epoch::Owned<Obj> as std::ops::DerefMut>::deref_mut` at /playground/.cargo/registry/src/index.crates.io-6f17d22bba15001f/crossbeam-epoch-0.9.15/src/atomic.rs:1250:18: 1250:35
note: inside closure
   --> src/main.rs:20:21
    |
20  |                     new_obj.count += 1;
    |                     ^^^^^^^^^^^^^
    = note: inside `crossbeam_epoch::Atomic::<Obj>::fetch_update::<'_, {closure@src/main.rs:18:89: 18:98}>` at /playground/.cargo/registry/src/index.crates.io-6f17d22bba15001f/crossbeam-epoch-0.9.15/src/atomic.rs:634:32: 634:42
note: inside closure
   --> src/main.rs:18:23
    |
18  |                   match obj_clone.fetch_update(Ordering::SeqCst, Ordering::SeqCst, guard, |old_obj| {
    |  _______________________^
19  | |                     let mut new_obj = unsafe { old_obj.into_owned() };
20  | |                     new_obj.count += 1;
21  | |                     Some(new_obj.into_shared(guard))
22  | |                 }) {
    | |__________________^