Parity handles drive failures / read errors. If you have another reason why filesystem corruption happen (eg: bad memory), there's nothing that Parity can do to help you on that. Unraid is really no different than any other OS in that regards.
Your system share on both the cache and disk 1. It's impossible to determine where the docker.img file is actually stored, but it wouldn't be a bad idea to change the system share from Use Cache: only to instead be use cache: Prefer
Stop the VM and docker services in settings, then run Mover from the main tab. After its done, re-enable the services