Sorry, I don't follow your description. I think you're mixing score reel and score motor here. And what do you mean the bonus unit is clicking the reset relay? Do you mean they're both clicking on and off while the score motor turns? And which reset relay? There are three of them.

If the 1000 point relay is always energized that might explain why the game has trouble resetting. That might be a good place to start.

Also, check the wires on your match unit. On one side they're folded over in a way that some might be touching. Try bending all the wires so they stick straight out from the board.

The match function can be disabled by removing the jones plug adjustment. Try disabling it to see if that makes any difference.

/Mark

The 1000 point relay circuit looks complicated but all of the scoring comes through one of the five switches in red:
Space Mission 1000 pt relay (resized).jpg
If you block all five of those switches with bits of paper the 1000 point relay should relax. Then you can remove the paper bits one by one to see which path is sending power to the 1000 point relay.

You're right. I missed that part of the circuit at the other end of the schematic, connected by the brown-yellow wire:
Space Mission 1000 pt relay 2 (resized).jpg
So the OP would need to block seven switches, not five.

The Change relay is driven by the Match unit. As you advance the match unit the Change relay should toggle on an off. If your problem continues as the Change relay toggles on and off the playfield rollover switches are less likely to be the issue. Although a short of some kind on the Change, A, B or C relay switches is (top part of the schematic in reply #8) still possible.

Shorts are hard to track down. Problems at the switches are more likely but shorts can happen anywhere. You might try disconnecting various jones plugs to see if you can isolate the issue. For example if you disconnect the playfield jones plugs and the problem goes away your problem is likely on the playfield.

The problem is that you need to get through reset first. If you're lucky you might be able to manually latch the Game Over relay which should provide power to the 1000 point relay. If that works, unplug the game, disconnect some jones plugs, plug in the game and latch the Game Over relay again. If you try to mess with the jones plugs with the game on you're likely to give yourself a shock or short other things together.

Note that if you unplug some of the backbox jones plug the problem might go away not because the problem is in the back box, but because you've cut power to the 1000 point relay.

You'll have to try some experiments to see what clues you can gather.