Is BTRFS unstable? (Update: It's not unstable, the problem is probably something else)

Well, memtest ran for 6 hours, 4 passes, 0 errors… I know i didn’t test each stick individually, but if any were showing errors, then i’d decouple them and find out which one it is. Both seem fine so i don’t think i have to do that.

Now what? How do i test mainboard bus system?