How long have you had the game? Have you had any work done? Usually when this happens it is because a diode was soldered in the wrong way. Usually when a switch or two in the same column as the slam tilt is triggered along with another, it can cause a slam tilt. I have seen this happen on several games. If you look at your switches. The diodes should all have the band facing the same colored wore. Either solid or with a stripe.

So probably any switch in the white and violet family. Probably not ball trough. I would try activating several switches at once if you can't see he diodes clearly.

Any luck?