While you’re waiting for that, I’d also look at the smart data and write the output to a file, then check it again later to see if any of the numbers have changed, especially reallocated sectors, pending sectors, corrected and uncorrected errors, stuff like that.

Actually, I’m pretty sure that Proxmox will notify you of certain smart issues if you have emails configured.

You should also shut the host down and reseat the drives, and check the cables to make sure they’re all properly seated too. It’s possible that one has come loose but not enough to drop the link.