I'm not entirely sure, but I think boolexprs might leak if they arent destroyed after being used, so using functions like Filter(function <whateverfunction>) will cause leaks if they are plugged direcly into the GroupEnumUnitsInRange, pretty simple but annoying fix, because I have to go through and clean up all the area of effect spells or other triggers in the game that use filters.
In plain english, every time you cast a spell that effects more than one unit, you may or may not be creating a memory leak which could cause the game to slow down or fail entirely after a long enough time has passed.