Could be a CPU issue, or a CPU-Vidiot communications issue.
Are any of these working CPU's the Bally AS-2518-35's? The pin/video games, Baby Pac-Man, Granny and the Gators, require a modified version of that cpu: AS-2518-133 (IIRC something about the zero crossing detector circuitry & Pinwiki.com has info about swapping a resistor for a diode).
Also, eprom locations and jumpers can be troublesome when you want to swap the cpu boards around between different Bally games (see pinwiki again).
I've seen that jumbled video image before in another thread, and it is normal under some circumstances. Wrote about some tests done on my working game in the other thread. https://pinside.com/pinball/forum/topic/granny-and-the-gators-vidiot-deluxe-issue#post-4222090
EDIT: This working Granny game will start up well enough, when the Vidiot board is completely disconnected, to do the front door test button switch lamp and solenoid tests.
Strange post script, supposedly you have to replaced R113 with a small signal diode, (the -35 to -133 board conversion), but this Granny has been operating for 25 years with an unconverted 2518-35 board (borrowed from an Elektra pin).
