Faulty ribbon cable, cold soldier joints, bad scan be sockets.

Incorrect sounds/no reset:

Check in solenoid test that Sound pulses 9 to 13 produce a sound.

See http://pincoder.ca for advance (and free) diagnostic ROMs. Specifically, start by reading the notes for the 11-sounds ROM. It will give you an understanding of how sounds are activated and, in the case of the heartbeat, cancelled. You might be able to then diagnose your problem before having to actually create a test ROM chip.

The Williams built-in solenoid test will allow you to check each of the 5 "solenoid/sound" signals, but it wont be able to send the "cancel" signal. No matter, you can still use the williams diagnostic to test for the "Tilt, Wire Twang, Dizzy, Extremely short burp, and Short Laser" sounds. Those sounds will stop playing automatically, but if you can't get it to play one or more of them you likely have a driver board issue.

Those sounds originate from PIA4 (Pins PB0-PB4) and come out of the driver board on 2J9 (Pins 9,7,1,2,3 respectively). If you can't play all of the above 5 sounds then this is where you need to start looking.