I have a few, one of them I was setting a system that would run a storm in one of my maps. This system had a random timing system for thunder and lightning. The way it worked was every time it lightning it would call a random thunder sound to play. Well I put all the entities in wrote it out on paper to make sure i connected everything right, and then when I played the level when it thundered it stopped the rain, I am not sure why, so after some digging around I just changed some setting in my build and then recompiled seemed to fix it... but was rather weird.