02782_uniq_exact_parallel_merging_bug
01459_manual_write_to_replicas
01171_mv_select_insert_isolation_long

I did some research. Look at it:

https://play.clickhouse.com/play?user=play#c2VsZWN0IAp0b1N0YXJ0T2ZEYXkoY2hlY2tfc3RhcnRfdGltZSkgYXMgZCwgcXVhbnRpbGUoMC45OTkpKHRlc3RfZHVyYXRpb25fbXMgLyAxMDAwKQpmcm9tIGNoZWNrcyB3aGVyZSAnMjAyMy0wOS0wMScgPD0gY2hlY2tfc3RhcnRfdGltZSBhbmQgdGVzdF9uYW1lIGxpa2UgJyUwMjc4Ml91bmlxX2V4YWN0X3BhcmFsbGVsX21lcmdpbmdfYnVnJScgYW5kIHB1bGxfcmVxdWVzdF9udW1iZXIgPSAwIGFuZCB0ZXN0X3N0YXR1cyBpbiAoJ09LJykgYW5kIGNoZWNrX25hbWUgbGlrZSAnJShkZWJ1ZyklJyBncm91cCBieSBkIG9yZGVyIGJ5IGQg

That shows that02782_uniq_exact_parallel_merging_bug started to be slow at 2024-01-28 00:00:00.
p99 was around 200s, after that date p99 become around 560s. That is too close to the timeout.

Only Stateless Tests (debug) is affected. Stateless Tests (debug, s3 storage) surprisingly is fine.

If we go deep to find the commit.
Check on this commit is good ff473d4
Next check on this commit is bad a7483ec

There is an interesting commit between this two checks: #59290
Maybe, just maybe, the tests become slower after it.

I do not see any vivid problems during execution when those tests fail. They just do a lot of requests, it takes time to execute them with debug build.