What I was wondering is trigger is fine for most players, but only some of them have problem.I was thinking maybe the problem may be language/font of player's game since problem involves cinematics and quests.Because other actions seems too innocent for me to cause fatal error.But now you mentioned hardware stuff and destroying null effects, maybe.But I have a reason to believe it is not destroying null effect.It is either cinematic/disable control part or the part inside local block.Because (according to my friend)when two players in game who has problem, only the one who clicks gets fatal error.But I can't understand why any of them would cause crash.
By the way, that cinematic action is actually waits if you set last three parameters as "set", "t"(amount of time), "wait".