loop2 is the docker image, it needs to be recreated, it likely got corrupt because according to these errors one of the cache devices dropped offline in the past:
May 9 14:11:47 unraid-2 kernel: BTRFS info (device dm-13): bdev /dev/mapper/sdi1 errs: wr 37591, rd 21008, flush 1044, corrupt 1187, gen 0
You should run a scrub now and monitor for future issues, see here.