what is the best way to track down issues when the error comes from the module itself?

A first step would be to look at the line mentioned in the error message, in order to get an idea what that line and the surrounding code is trying to accomplish, what data is being processed, and how it tracks back to how you're using the module. This might give you some idea as to whether you're maybe passing incorrect parameters to a method, or some such.

Being able to do this is the big advantage of open source software...