This is mostly a straight refactoring of the existing code to work independently of specific member variables in the involved classes, using a bit of template magic to avoid redundancy and moving the work code into subfunctions.
It still needs some testing to see if it a) helps fix the crash issues and b) doesn't break anything-
These are rather small and extremely frequently allocated, so they are prime candidates for memory arena, because it not only avoids fragmentation and internal overhead due to mass allocation of small memory blocks but it also makes it a lot faster to free the memory when finishing a level.