Thanks for reply and help.
I’ll do as you propose and will secure erase the drive, not so easy since the system is in production mode already and gotta find a replacement first…
Could you elaborate which part of the SMART output told you about the bad blocks? Thanks!
edit: just checked the second NAS with identical hardware. It has the same exceptions in the syslog. Can this really be a coincidence that two drives from the same model both throw the same errors inside the syslog?
Anything I can try before I blame the hardware?