Using the tag report tool to report tags with Quality: Error_Configuration, and I'm getting results like this:
These particular tags are nested UDT instances within another UDT (nested within the tank UDT) and the UDT instances themselves are set to disabled, e.g. quality = Bad_Disabled.
I'm also getting other results for UDT instances which don't appear to have any errors with them at all looking at the tags within them and at the UDT instance itself. There is one tag that is disabled, but that's about it.