Try resetting the ribbon cable to display first. Pull and then reattach. Do same with all of the connectors to display as well. Pull off gently, then put back on firmly. During this, inspect all those wires that they are in those prawns in connectors firmly, nothing looks loose.
I have a Jokerz, Fire, and Riverboat gambler and they all have similar displays. Fire is 4 panel but same connectors.
If you just moved it, or been a while since you played, bor played a lot, they jiggle loose and you get what your describing.
Start there and will go to tje board if needed. On older system 11s this is common.
Had a bunch.