The diagnostics show that there appears to be corruption on the cache drive itself, and internally within the docker.img file (the loop device which is presumably on the same drive). You need to fix the cache level before attempting to fix the docker.img level. Probably best to start with a scrub of the cache drive to see how that goes.
Instructions for recreating/repopulating the docker.img file are here in the online documentation accessible via the Manual link at the bottom of the Unraid GUI.