This

Thanks, I'll try that. I loaded the drive using dd a couple of times, and that did bring the system down a couple of times. I was writing to the filesystem though, while the system was booted

Unfortunately I have no other system at hand at the moment that's able to accept nvme drives :( I could try using windows for a couple of days see whether the issue is really linux-related, but I am trying to avoid that lol

Happens with both drives, I have tried each possible permutation (Samsung in slot 1 and 2, kioxia in slot 1 and 2, and even only installing one drive at a time)

Danke!