Readying TrueNAS 13 to 24 upgrade and found files that have correct permissions but won't delete

I had a similar problem in TrueNAS 12 (I couldn’t even delete the files as root user) but that was solved by upgrading to 13.3; Thanks once again to @awalkerix advice:

Looking at the vfs objects’ settings may help provide a clue.

If you’re on 13.0 then going to 13.3 first might help?