Full diagnostics are always better, but the issue is
Dec 6 11:51:22 Tower kernel: BTRFS info (device loop2): bdev /dev/loop2 errs: wr 2283, rd 0, flush 0, corrupt 0, gen 0
Dec 6 11:51:22 Tower kernel: BTRFS info (device loop2): start tree-log replay
Dec 6 11:51:23 Tower kernel: BTRFS critical (device loop2): corrupt leaf: root=2 block=340262912 slot=37, unexpected item end, have 3426207789 expect 15062
Dec 6 11:51:23 Tower kernel: BTRFS critical (device loop2): corrupt leaf: root=2 block=340262912 slot=37, unexpected item end, have 3426207789 expect 15062
Dec 6 11:51:23 Tower kernel: BTRFS: error (device loop2) in __btrfs_free_extent:6805: errno=-5 IO failure
Dec 6 11:51:23 Tower kernel: BTRFS: error (device loop2) in btrfs_run_delayed_refs:2935: errno=-5 IO failure
Dec 6 11:51:23 Tower kernel: BTRFS: error (device loop2) in btrfs_replay_log:2281: errno=-5 IO failure (Failed to recover log tree)
Sight unseen without diagnostics, you have to delete and recreate the image. https://forums.unraid.net/topic/57181-docker-faq/#comment-564309