Concur, sounds like game is going into tilt. Does tilt show as closed in switch test?

There are 3 tilt switches in the game. The plumb bob, roll cage just above it, and a swing tilt on the bottom of the playfield. Inspect them, then as zombywoof says, cut off the cap by the bob tilt and see if that clears the problem.

You may have an MPU connector issue if you cant get the game to go into self test. You'll need to fix that ASAP or it will be difficult to work on other issues. Examine J3-1 as that is the input for the test button.