Had a quick look on your post at blender.org forum. As already stated, using third party extensions make it more difficult to make out a solution.
Most probably there are something about this extension that causes Blender to crash rather than a bug in Blender itself. I therefore suggest you try to reach out to the creator of that particular extension.
I don't know anything about this extension, if it is just a bounch of files to be extracted in Blender folder (where blender.exe are located or some related sub folder) then you can get a portableapp version of Blender. This make you able to test if the issue are caused by:
Need a different (older) version of Blender.
Some settings in Blender (portableapps programs have their own local folder where all settings are stored and doesn't share with rest of the system)
I haven't done any resource on your plugin, but if it in fact are abandondware as you're probably correct about, then I'm afraid there is nothing I can do to help, and there is nothing the Blender team can do to help either.
The only probable solution is to report a bug to the makers of Source Filmmaker, but if that software are abandoned, that will never happen.
Hope you're able to find an alternative software that make you able to do your work 😎