A very common problem with Gottlieb solid state machines is that the coin
door slam tilt switch or the roll ball tilt switch gets bent or dirty and
puts the machine in perpetual tilt. Check to see that these switches are
normally closed and have good contact. These are low voltage gold-plated
switches and should never be filed, only cleaned with a stiff paper such as
a business card.
If you are fed up with these switches failing you can just solder a jumper
from them directly to ground, eliminating this problem forever.