To answer myself and help anyone else, votdev has the correct answer...
You are surely using '/sharedfolders/xxx' in a plugin, e.g. Docker. This is not allowed because it results in the problems you now have. The '/sharedfolders' shortcuts were only implemented to make navigation on CLI easier. Using them for example in Docker means that Docker locks the dirs and systemd fails when OMV tells it to reload them.
So, change plugins to use eg. /srv/dev-disk-by-label-Media/Media instead of /sharedfolders/Media