you're supposed to get all of the 4 dead ends, then the true end will play automatically. If you got an explosion with an item you should try again cause the explosion actually is a random occurence from what i can see
The explosion happens every time though. Maybe 30% is too high a chance?
EDIT: I tried it again. I finally got a different result. In fact, they all worked this time and I was quickly delivered into the next part of the game.