I wonder whether this problem is because your NAS isn’t talking properly to your Unitiserve. You could go into the NAS setup and check that SMB1 hasn’t been disabled. Unitiserve needs SMB1 and some OS have changed the default to SMB1 off, for security reasons.
Having the same issues as yourself, latest software was already installed in my case so guessed that wasn’t the problem, though necessary to move forward.
At present I am still converting from WAV to FLAC ( still over 25,000 tracks to go) so don’t want to mess with it.