Mouse Tweaks clicks the containers' slots via reflection, so when the container code throws, the crash log looks kinda like it was Mouse Tweaks which crashed. There have been multiple crash reports (#14, #7) which were actually bugs in the container, but were erroneously thought to be caused by Mouse Tweaks due to the unclear logs.

It should be documented somewhere (perhaps in the issue template? And also in the handleMouseClick() threw an exception when called from MouseTweaks. message?) that those kinds of crashes are usually not Mouse Tweaks' fault, and where to find the relevant stack trace.

e7d7350 replaced reflection with mixin accessors which should hopefully give clearer backtraces.