Work out which files/folders are causing it. That will probably provide clues about likely causes. e.g. If it's a folder full of videos then it's probably a video codec going wrong.
There isn't a special debug version of Opus in general. Every so often one might be made with code to help diagnose very specific issues, or to test new changes before release, but those are one-offs and not generally useful or maintained.
There are debug settings you can turn on in the normal version of Opus, however. Those should be mentioned in the relevant FAQs for the issues they help resolve. (e.g. The Context Menu debug setting is mentioned in the FAQ about diagnosing crashes related to context menus.)