From Debian Bug report logs - #940105:
There were some reports over the last weeks from users on linux-btrfs which suffered from catastrophic btrfs corruption.
The bug which is apparently a regression introduced in 5.2 has now been found[0] an a patch is available[1].
Since it's unclear how long it will take to be part of a stable release and when Debian will pick this up in unstable, please consider to cherry-pick the patch.
- [0] lore.kernel.org
- [1] patchwork.kernel.org