My bigfoot stopped turning its head again so I started troubleshooting.
The motor turns when energised by a 9 volt battery. The connections from the motor to the bi-directional motor board show 0 ohms from end to end.
When I put the game in Bigfoot head test I measure 12,5 DC volts between the pins on the bi-directional motor board's J2 pins that feed the Bigfoot motor. However when I then put the connector on the J2 with the leads to the motor the voltage drops to about 0V. This seems strange because when I test the voltage on the 9V battery when driving the motor it stays about 9v. Does this mean the bi-directional motor board is bad?
Thanks in advance!

It's probably not that. Last year I replaced the cap and checked the traces on the board. The board also seems to switch the output to the J2 on and off as it should.
It just doesn't seem to be able to hold the voltage under load.

Wow, that’s good info Generalgman! Great video. I will test the way that guy explained and see what I can come up with.

Well, I measured some things. Unfortunately I found no voltage drop between the bi-directional board J2 and Bigfoot on either of the two wires so I don't think it's a bad connection there.
I also measured the supply voltage to the bd board on J1 and that stayed at 13,5V with the Bigfoot motor switched on and off so maybe the problem is on the board after all.