Thanks for the reply Steve !
I already tried to compile Slicer in Debug mode, but I ran into the link issue with Python still being in Release (similar issue here but with SimpleITK).
Error LNK1104 cannot open file 'python36.lib' [D:\...\build\Slicer\CTK-build\PythonQt-build\PythonQt.vcxproj]
Unfortunately, my module relies on PythonQt so I cannot just disable the dependency.
So, in the meantime, I guess I’m stuck with trying to figure out the bug by progressively dismantling my code, which is still very tedious given the rare occurrence of the crash.