Just a few days ago I've had a checksum mismatch on a RAID-1 setup, on the metadata in both devices, which is very confusing.

Over the last one or two years I've experienced twice a checksum mismatch on the file storing the memory of a VMWare Workstation virtual machine.

Both are very likely bugs in Btrfs, and it's very unlikely that have been caused by the user (me).

In the relatively far past (around 5 years ago), I've had the system (root being on Btrfs) turning unbootable for no obvious reason, a couple of times.