With studio’s regular tools or with plain ol’ plugin:Union(), the attached selection doesn’t crash studio (just errors). When unioned with this plugin though, Studio crashes with “An unexpected error occurred and ROBLOX needs to quit.” Even though it only crashes when that plugin tries to union it (not the default tool), I don’t imagine CSG is supposed to crash studio ever, so thought I’d post this here in case there’s some elusive, rarely-occurring bug that this repro might be able to help squash.
If I select the parts in that place and click Intersect, it tells me that the CSG cannot be made (which is the same as doing it manually) and then adds a bunch of extra parts. It appears the plugin is not catching errors or cleaning up when it fails, but not crashing.
There are two parts of the plugin. One is Intersect and the other one is Brute Force. I never added in a button for the latter because it was quicker to just Ctrl+Shift+G. To use the brute force (what causes the crash), rebind the default union hotkey to something else (I prefer Shift+G) and then use Ctrl+Shift+G on the selection.
Sidenote: I should probably add a button for brute forcing because a lot of people think that it only does intersecting