I would look at your power supply voltages. Remove the Power Supply and the PPB board and check the solder joints on the connectors and the fuse holders. Resolder as necessary.
Also look at the connectors and look for any burnt ones to fix on either of these boards while you have it out.
Your +5 volts is probably low when this happens to your game.
Download the manual here for reference:
http://mirror2.ipdb.org/files/2848/Baywatch_Manual.pdf