sure, I was unable to make it crash when compiled with debug symbols. without that (a meaningful backtrace) there is nothing I can do.

And honestly, I don't really think it is a problem in cssu-thumb packages, rather a bug in the application. Why not file a bug against it? As your statement "i'm getting used to hold the pause button a little longer" leads me to believe there is some race condition in the application, triggered by -thumb being faster/slower.