Hi @<1523701087100473344:profile|SuccessfulKoala55> , thanks for responding. I've found out that my first error came from cloning a super old version of the clean up task in the web UI 😄
I don't know about the other error, to me it looks like the task gets deleted before handling errors, but since an error occurred (some 404 stuff, maybe the files actually aren't there) when deleting some artifacts on the task, clearml tries to reload the task and fails, with the 400/201 or 400/101. Something like this:

Deleting 

 with type artifact
2024-01-05 14:08:14,675 - clearml.storage - WARNING - Failed deleting object /myproject/testing/alternating-stick.5deba388a0a1416f8b24e760813f4080/artifacts/config-file/config.yaml (404): File /mnt/fileserver/myproject/testing/alternating-stick.5deba388a0a1416f8b24e760813f4080/artifacts/config-file/config.yaml not found
2024-01-05 14:08:14,679 - clearml.Task - ERROR - Failed deleting the following URIs:

2024-01-05 14:08:14,703 - clearml.Task - ERROR - Action failed <400/101: tasks.get_by_id/v1.0 (Invalid task id: id=589f573a250a4af4acf016762deb5141, company=d1bd92a3b039400cbafc60a7a5b1e52b)> (task=589f573a250a4af4acf016762deb5141)
2024-01-05 14:08:14,706 - clearml.Task - ERROR - Failed reloading task 589f573a250a4af4acf016762deb5141
2024-01-05 14:08:14,725 - clearml.Task - ERROR - Action failed <400/101: tasks.get_by_id/v1.0 (Invalid task id: id=589f573a250a4af4acf016762deb5141, company=d1bd92a3b039400cbafc60a7a5b1e52b)> (task=589f573a250a4af4acf016762deb5141)
2024-01-05 14:08:14,726 - clearml.Task - ERROR - Failed reloading task 589f573a250a4af4acf016762deb5141

Does that sound plausible to you?