Hi Rob,
On Data East games if the outhole coil is firing when a switch is triggering, this is normally caused by a fault on the PPB board. This board shares transistors between flashers and coils and the relay selects between the two. If the relay is not working then coils will firing instead of flashers being triggered. The relay can go faulty but the most common cause is dry joints on the relay or dry joints on the headers pins which lead to the relay. The Tip36C also tend to fail if there was a faulty coil in the game.  Also worth checking the GI connectors on the PPB and PSU while you have them out.

Also quite common for the 6821 to fail in this game. The easiest way to test these are to burn a copy of Leon's DE Test Rom from www.pinrepair.com With this Rom installed it will toggle all the inputs/outputs of the 6 PIAs so you can test these with a logic probe. Make sure the board does is not connected in the game while running the Test Rom.

regards Derek