RAID1 has been fine for years, but hardly anyone is running that and RAID5/6 are still considered unstable even by the devs: https://btrfs.readthedocs.io/en/latest/Status.html#block-gro...
I ran into Btrfs RAID6 corruption myself about ten years ago. Though to btrfs's credit, I didn't lose any data: the filesystem only locked up read-only on me. But this time I'll take their word on unstable.