I had a BTRFS raid corrupt because one of my HDD had a firmware bug and was silently discarding writes.
Sure... HDDs shouldn't do that, but it's literally the job of a BTRFS raid to protect me from such issues. The data was all still intact on the other drive. I could see it with dd, but BTRFS refused to read it.
YES!!! Sorry to beat a dead horse, but it has been so frustrating for me. I thought I did something wrong, like, how could the partition break for doing nothing! Where did I fucked up? I cannot imagine the experience with a RAIDed BTRFS array shudders