Except the knocker reset could be unrelated. I would start replacing ribbon cables first. I would consider testing the knocker in the solenoid test menu. If firing it there causes a game reset, you may have a diode issue. Since the knocker really isn't required for game play and is often annoying to many, I might just detach it in the backbox and consider that issue solved.

There is no direct relationship between the display and the flippers. It does sound like the CPU board is losing general communication with the rest of the system. The ribbon cables are responsible for that. The same ribbon cable runs from CPU board to fliptronics board to audio to video. If replacing that doesn't help, I might reflow solder on the CPU board pins on that cable and reseat the CPU, itself. Any battery leakage on the CPU board?

How is input power to the machine? Is it sharing a circuit with a microwave or a/c unit? Williams machines are very input power sensitive.