Doubtful it is a 5V issue, but if your meter has a min/max setting, use it. Power up the game and clip your meter to the 5V and GND test points. Press min/max and begin to play. When the error occurs, go back and read the meter and see if the 5V dropped for some reason.

In the video, you're just creating a low impedance path with your body which causes chaos with the switch matrix.

I'm thinking the same may be happening during game play. Something loose or something that is not grounded properly on your side rails, coin door, trim pieces etc. Make sure your ground braid is intact and touching everything including leg bolt brackets.