Many questions about Diffractor are answered in the documentation.
Diffractor has an issue tracker on Github where bugs or enhancements can be reported or discussed. This is the best place to get help.
If Diffractor is crashing, crash reports are automatically sent (if you have the ‘send diagnostics’ option enabled). All crash reports for the current version are investigated. If a fix is released, Diffractor can automatically update (if the ‘Automatically install updates’ option is enabled). In Diffractor, press F6 to see these options.
Diffractor is an open-source program. If you know C++ you can fix issues yourself. The source code is here.