Just so I'm clear here. You can activate the Right flippers indefinitely and the game works fine. If you activate the Left Flippers the game will lock up in 3 or so flips? I'm assuming you're in test mode as well?

Ok, so 1st, lets remove game play from the equation. I'm looking to see if activation of either flipper (on it's own) will reset the game. So, no balls in play. She/you can start a game but don't plunge the ball into the playfield. Just activate the flippers.

On the note of intermittent flippers:
The upper/lower flippers are on 2 different switches stacked on top of each other mounted on the side of the cabinet. If you slowly push in a flipper button you should be able to get the lower flipper to activate without the upper. These flipper switches pull full voltage/current so they will pit/burn out over time and either need replaced or resurfaced. Or, she simply didn't push the flipper button in far enough. If the former:

With the game turned off you can slip some 120 or higher grit sandpaper (nail file will work too) in between the contacts. Gently press the contacts together (from inside the cab) and move the sandpaper back and forth a few times. Do this to both contacts. If the contacts are pitted this should help with intermittent activation in the short run.
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So the issue here is being sure... your wife was playing a game at the time so something else may have happened when she thought she was hitting the right flipper only.

The key to successfully troubleshooting is taking a single sample at a time. If we mix up multiple things all at once then we don't have real information and we just circle the drain.

I'm trying to determine if only one flipper circuit causes the issue. It sounds like the left does it all the time on its own. I'd like to know for sure if the right does to, and if so how often. That's useful data.

So the flippers don't appear to be the cause from my POV. Can you describe the crash symptoms? Does it freeze, do the lights go out, displays top?? That kind of stuff. Or does it reset?

I'm interested in the fact that you couldn't start a game after it crashed. Did you check/test the start and trough switches to see if they were operating? It's been a few years since I owned a BK so I'm running on failing memories about the requirements to start a game on Sys7.

Does it work again if you leave it for a few hours?

To continue Schwaggs questions... how do the Power supply connectors look? Burned?

Well in the classic sense of the term yes, but I didn't have a definition from him at that time as to the actual state of the machine and simply stuck with the terminology he was using.

It would appear that the game is still executing code (thus not actually crashed). The blinking lights and display are that of the game you were currently playing? Or did it return to an attract mode type of lights/score display scheme?

So it doesn't work at all now? That's easier to debug than intermittent issues. So when you turn it on is it running attract mode and it's not starting a game when you press start? Put it into test mode and see if it's registering the start switch and that it sees 3 balls as slochar mentioned.

It's easy to miss things when you're moving quickly and concentrating on a different symptom. It would seem logical that the game could have booted into audit mode but you classified it as a crash (you weren't expecting audit mode) and power cycled again. Which would have cleared and moved you into Attract mode. Thus, it seemed like a crash and a reboot to recover.

I'd like to see us work through the game starting issue before we work back to the "crash" issue. Trying to solve multiple problems at once is going to get confusing quickly.

Put a business card (or card stock/etc) in between the contacts of the cabinet flipper switches, one flipper at a time, and see if the game resets on only one of the flippers or both.

The EOS switch on the lower playfield flipper in your pic looks wrong. Can you get a better shot of that?

Yea, that's ok... to me it looked like someone used a newer style switch in that mech.

Ok, so it only fails when BOTH Upper/Lower flippers on the Left are activated at the same time. Seems like a load issue but it's odd that it's not happening with the right. (I'm still not clear on this even after reading the thread again) I wonder if one of the flipper coils has some shorted windings and is loading down the PS. Do you have a multimeter to test the coil resistance?

When is the new power supply arriving?

I'm kinda hung up on the flippers causing this ATM.. Have you ever measured the resistance of the 2 windings of each of the flipper coils and compared them to known good coils?

I know it's a PITA to unsolder coils to do this.. Here's the flipper schematics, you might be able to unplug certain connectors and isolate them without removing them but you'd still need to slip a business card in the EOS switch to remove it from the resistance test of the hold winding.

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These are supposed to be series coils, thus I'd expect one of the readings to be the sum of the 2 other. Yea I get that there's going to be some variation but upper right went down?

Are the winding wires securely soldered to the lugs?