Quoted from wayout440:

I actually had about the same problem...with my F-14. Went 'round and 'round with the usual stuff, replacing diodes etc... still had the mysterious random tilts. I finally found that the upper "T" target was causing the tilts. Did the usual diode replacement again on that target. Still tilts.
I took the target switch out and ohm'd it for continuity and proper operation and it appeared to work fine out of the game. Reinstalled it and guess what - still tilted! I ordered a new switch and replaced it, and the problem was gone for good. I never knew what exactly within the switch was causing it, but I suspect that perhaps the rivet through the "sandwich" of the switch base was probably shorting somehow, I just never saw it with a meter.
I assume that your Fire right flipper has a lane change switch off of the cabinet switch. Try replacing the switch along with the diode, unless I am wrong about Fire and your matrix switch triggered by the right flipper is off of the right flipper EOS.