I can't seem to reproduce this. Did you make sure to use the "From WAD File" tab when adding the resource?
If so, what is the name of the SOC file(s) in the WAD that doesn't work? In WAD files, UZB should be checking for any MAINCFG, OBJCTCFG or SOC_-prefixed files.
Hmm, while I do notice the issue with UZB only reading one SOC_-prefixed file, I can't reproduce the issue where having a map present interferes with SOC loading.