Any game that was shipped 2000 miles likely will have some parts loosened here and there.
That includes socketed parts on the CCPU logic board and the monitor chassis. Also, the ribbon connectors and all power MOLEX etc.
And those breakers on the power supply can be problematic - should reset them to make sure the flickering is not associated with the monitor power rails.
All that said, the CCPU logic test only needs the +5VDC to validate the board working and the LED to turn off.
The CONDOR type power supplies don't usually report issues from collectors that they have excessive AC ripple on the 5V rail. Mainly bad breakers as mentioned.
The supply also sends a simple SPOT KILLER signal (voltage) to the monitor. Keep that in mind.
On most CCPU (without the HSS mod) the 5101 RAM is typically not socketed; They're soldered into the board. The ROMs are socketed. Similarly on the monitor chassis some parts are socketed. All should be reviewed.
The OPs description does not really help define if the cabinet is "playing blind". That's one place to start (with monitor disconnected and game credited, playing and making correct game sounds etc). Take it slowly and do proper step-by-step test method to find the issue.
As always -> YMMV.
