One of the ways to complete a quest I've been fixing up sets a stage which sets all the NPC's travel package to run for a trigger box. When each one hits the trigger box I grab their reference disable them and increment a quest script counter, trouble is that's been failing the NPC's are all getting disabled but this quest variable isn't being incremented for each one. The NPC's are tending to enter the box in quick succession and I'm wondering if it's too much for the trigger?

I have solved it by checking their enabled state in the quest script itself but it seems a lot less efficient than ticking them off with the trigger block.