Quoted from stangbat:
Regarding the catapult eject being weak, below is what I've found after having my MMR on location for over a year.
Occasionally the moat eject and usually the castle destruct would get weak or quit working. Lately it is the castle destruct coil that gets flaky after 1-2 weeks. I checked connections, repinned connectors, tried various different things and the problem would always come back. I finally figured out the issue, and the same issue could be affecting your catapult strength.
The small driver board that contains the transistors sits on standoffs above the large playfield PCB that has the insert LEDs. Data is passed to the driver board through 0.1" header pins. The pins are on the driver board and push down through a 0.1" socket on the large playfield PCB. The pins are located under the chip that is on the driver board PCB. The solution is to push down and wiggle this connection to make sure you are getting good contact. After doing this my moat problems went away and my castle destruct works fine for a couple weeks but eventually it starts getting flaky again.
I don't have a good picture of what I'm describing, but I did find a pic and I've highlighted the chip that has the connector underneath it. See below.
At some point I'll fix it for good by changing the pins and socket. But right now since the game is on location I raise the playfield every couple of weeks and push/wiggle the connector and the problem goes away. This may not be your problem, but give it a try and see if it helps.
Would turning off the shaker motor help (if you haven't already done this)?