Didn't download your capx but I've encountered a similar problem so i'll try to help.
Line 1 : remove npc destroy action
Line 2 : no change
Line 3 : duplicated line 2, change instance to 1
Section Pick Nth instance
Now what if the running npc collides with 2 npcs at the same time on the same tick and you have to destroy all three.
Idk? Is that possible idk? Is there a system expression showing how many instances of a trigger are created per tick, idk?