When I was having my phantom pie problem initially, I also honed in on the "moving objects" chip on the PCB. I cleaned my chips relentlessly and was frustrated that nothing I did seemed to fix the problem.
I brought my boards over to someone else's house to use in their DK machine, and the problem didn't happen. At my apartment in my DK machine, I could see the glitchy pies on every pie factory level I played, if I just hung around long enough to see them. Using my boards in someone else's machine, I played 5 or more games and never saw a single phantom pie.
I returned home and put my boards in my DK machine, and the pies were present immediately. I was convinced it wasn't a board issue.
I cleaned the contacts between my power supply and the wires connecting to my PCBs, and the problem appeared to go away. It stayed away for 4 months, and then I became frustrated when the glitchy pies reappeared.
I had been moving my DK machine around in order to get behind it for the TwinGalaxies recording rules, and I wondered if maybe moving it around had caused the phantom pies to reappear.
What I ended up doing was following a suggestion by Dr.Detroit, who had some success cleaning Nintendo power supplies using some Simple Green cleanser, allowing the PS to dry completely, and then testing the voltage again before reattaching the wires to the boards.
Using a multimeter, I documented the voltages and compared them to the DK manual:
9P connector:
1brown gnd
2red gnd
3orange gnd
4yellow +12v (multimeter read 12.0/11.9)
5green +12v (multimeter read 12.0/11.9
6blue +5v (multimeter read 5.1)
7purple +5v (multimeter read 5.1)
8gray -5v (multimeter read -5.1)
9white +24v (multimeter read 23.6)
10P connector:
1brown -5v (multimeter read -5.1)
2red -5v (multimeter read -5.1)
3orange -5v (multimeter read -5.1)
4yellow -5v (multimeter read -5.1)
5green gnd
6blue gnd
7purple gnd
8gray gnd
9white +5v (multimeter read 5.1)
10black +5v (multimeter read 5.1)
...
I decided that since Dr.Detroit had some success taking his PS apart and cleaning it, that I would do the same. With the multimeter, I felt like I had nothing to lose. After I cleaned it I could test the voltages again before hooking up my PCBs, so I wouldn't risk the life of my game. In a worst case scenario, I'd have ruined my power supply, which I could replace. In a best case scenario, my glitchy pies would be gone. And in a realistic scenario, I'd have cleaned the power supply with no change to my glitchy pie behavior, meaning that I now knew that cleaning the power supply made no difference.
I reassembled the power supply this morning and the voltages were all safe. When I reattached the game and monitor, and played through the game, the pies were gone again.
I've only played about 5 games, but the problem seems to be fixed. It's always a little tricky at this point since "absence of evidence is not evidence of absence," but before cleaning the pie problem was consistent and immediate. Now the game seems to be working 100%
A thorough description of what I did, following Dr.Detroit's recommendations:
Removed wires connecting power supply to PCBs and monitor.
Powered on switch and recorded voltages using multimeter.
Powered off game, removed power supply
Separated power supply halves, removed wire connectors holding two halves together
Sprayed PS circuitboards thoroughly with Simple Green, diluted with water 1:1
Let stand 20 minutes
Rinsed PS circuitboards thoroughly in sink using water spray nozzle
Dried with blow dryer until all traces of liquid that pooled were gone
Sprayed electronics cleaner in 6 ends of the 3 wires removed from PS
Let air dry 24 hours
Reassembled PS
Remounted PS in cabinet, replaced ground cable
Reconnected power wire from transformer/switch, but DID NOT RECONNECT WIRES TO GAME PCBs OR MONITOR
Powered on PS
Tested voltages, confirmed were same from what I had previously recorded
Powered off cab, reconnected everything
Powered on game and tested for glitches
It seems to have worked, although I'm keeping my eye out for a while.
You mentioned that you had another Nintendo power supply. Have you thought to try swapping that into your DK cab to see if the phantom barrels still happen?