I added dupfinder as a command runner to a third project. It scans *.cs files in directories, excluding *.g.cs and *.designer.cs, and by switching on debug I see it finds the relevant files.
In the dpulicates view I see approximately what I expect in terms of detected dupes, but selecting an instance in the center listbox yields "null" in both left and right file pane.
All three projects use the same repository (Perforce) and have the same charset. The first two projects work like a charm. The log says nothing about things going wrong.
What can be happening? I run TC6.0.1