This is an interesting one. I am not sure what to do about it, if anything.
I downloaded the module and it looks like the developer has manually edited the buildfile and changed the integer StackMetrics fields to non-integers (0.25, 0.5). The Stackmetrics Configurer uses IntConfigurers, so these values cannot be added via the Editor.
v3.0.17 failed quietly and supplied some vaguely reasonable default values. v3.1 fails with an IllegalBuildException and generates a bug report.
I’m thinking we should do something like the BadDataReport, but slightly different - (like ‘Your module designer is an idiot, he did this…’).
Technically, bad data in the buildFile is a module error, so BadDataReport is appropriate. Unless of course VASSAL wrote that data in the first place, in which case it should generate a bug report. The involved solution would be for VASSAL to write a checksum of the buildFile into the metadata when saving. Then it could detect whether the buildFile was hand-edited or not and generate a bug report or not. The easier solution is to just code to the most common case, which is to assume that VASSAL wrote the data and file a bug report.