Comment by homebrewer

raid 5/6 is completely broken and there's not much interest in fixing it — nobody who's willing to pay for its development (which includes Facebook, SUSE, Oracle, and WD) uses raid 5/6; you shouldn't have been running it in the first place. I understand it's basically blaming the victim, but doing at least some research on the filesystem before starting to use it is a good idea in any case.

https://btrfs.readthedocs.io/en/latest/Status.html

edit: just checked, it says the same thing in man pages — not for production use, testing/development only.