This issue is consistently reproducible. Config and stack traces are in the comments.

While running test/format with disagg enabled an eviction thread is observed waiting on a mutex in palm. However, no thread in the stack traces seems to be holding this lock which suggests a potential bug where the owner thread may have exited prematurely or failed to release the mutex.

Eviction thread waiting on the mutex has an exclusively lock to the ref (like it should), preventing any other thread from proceeding to access the page. This causes test/format to simply hang.