Ruling: Too many balls in the machine.

I needed to make a ruling yesterday that was interesting on a couple fronts. Here is has it played out (even the the title is a spoiler) when I was called over.

Player 3 ends ball 3. Ball is kicked into shooter lane and game is over. Player 4 gets no ball. Ok, easy. Give them a compensation ball on a new game. Plunge ball and the ball will not kick of of trough, coil starts overheating. Unfortunately, player 4 donated the machine and is the one to look at it. I tried starting with ball already in shooter lane, then it kicked a second ball. We ruled catastrophic malfunction and they play a new game.

While they are playing, we keep looking at the game and realize there is a fifth ball. Remove it and everything now works. Clearly I can’t undo my previously ruling, so that is where things ended.

What I think is interesting is what if I had figured this out. Clearly, there was a stuck ball, and someone added another ball to the machine. It came loose during player 3s ball. They happened to simultaneously drain and not have this prematurely end their ball.

Would having 4 balls installed automatically make the entire game a catastrophic malfunction, or if I had figured it out should I have removed the ball and given a compensation ball?

How do you deal with conflict of interest on risk of damage to donated machine (in this case, the coil overheating)?