Missing lowedir

TrueNAS Core with Ubuntu 20.04LTS & Docker v20.10.7 VM running nginx/portainer/nextcloud started coming up with overlaysf ‘missing lowerdir’ message. Posts elsewhere suggest removing and reinstalling docker. Is there no way to correct the error through a configuration file somewhere. I think I looked at the overlaysf layout following a suggestion in another blog and amongst the text saw reference to lowerdir followed by text so I assume it is there. Portainer & nextcloud appear to be working in that I’m moving files in and out of nextcloud but haven’t committed to putting all my media there whilst this message appears.

Complete noob with Linux