I just had a similar issue with my Mousin Around machine except all the GI was out. The culprit was a Rottendog interconnect board... or actually my installation of it. One of the pins that supplies the GI was properly connected, when I fixed this, only half of the GI worked.
The issue similar to yours was fixed when I stumbled across this page:
If you look at the following image from that page:
"The GI circuits coming directly from the transformer enter the board on the right side at connector J6. The top 4 wires are yellow and the lower 4 wires are yellow with a white trace. In actuality, the GI wires are only 4 wires, instead of 8 wires. Once the upper 2 wires reach the board, each of them are daisy-chained through the insulation displacement connector (IDC)."
On my replacement board, it didn't have the daisy-chained wires that were soldered under the board. Once I replaced these wires, everything worked.