I've got a weird problem with a D&D pinball machine, every 4 or 5 plays the game will launch all 3 balls into the trough at some point during the play. Then, usually one or two of them will get stuck in the bottom and the error message "check FU1 or Field Fuse" will display. Upon removing the balls from blocking and turning off and back on the machine, the error message will subside for 4 or 5 more plays. Is this a common issue? If I change the fuse will that solve the issue or is there generally some other underlying problem that causes this to happen that I need to look for as well?

To be honest, I'm not sure what the FU1 and playfield fuses protect.

I can't find in the manual exactly what it protects, but from my limited ability to read schematics and wiring diagrams it seems to run in line with a diode bridge, a couple of solenoids and a +43V relay. Sorry I'm horrible for info, I'm mostly just trying to compile as much information as I can, so when I do get a repair guy to look at it, it's not just a hodgepodge of troubleshooting.

I've checked the fuses and that didn't work, so I took the advice of a repair guy I know and swapped the fuse board with a project D&D I've got and that didn't fix the problem either. Is there anyone else who ran into this same sort of situation?