Last week, I discovered that a fluid in my mod (the freezing water) causes crash. It's a simple fluid that adds potions effects to the entities that collide it based on the items they have in hand.
This was caused by the fact that items and other non-living entities can collide it causing crash. I later fixed this problem by adding a condition that checks if the entity is not an item, an xp orn, a falling block, etc.
If you add the procedure block "is entity a living entity" these crashes would be prevented and we wouldn't have to make a big list of entities that aren't affected by the procedure.