Aha, you’ve added a log to your post; good idea. This is likely the cause of your problem:
That’s an EXT4 filing system error. This forum seems to be seeing a few folks who’re running self-managed Postgres with FS corruption.
I’d suggest examining your options to see if fsck can be run on the volume, though a Fly employee on the other thread says that is not possible as of January. If you can’t access a mountable filing system, maybe ping Support instead.