1) What other switches are being lazy? Identifying this could help isolate the problem by using the cross matrix diagram.
2) What resistor fell off and on what lamp board? Pic would help. Not sure if you are describing a warming resistor. If it's warming resistor and you replaced your 89s (FLASHERS) with LEDS then no, you dont have to put it back. In fact, you are suppose to remove them all if you run LED'S in your flashers or else they will not function properly.
3) What do you mean it resets itself? Do you mean its "tilting"?

#1 & #3 sounds like you have a bad diode on a switch somewhere under the playfield allowing current to run back onto the "tilt" circuit.

1)That is a warming resistor that fell off. You only have to remove the two outside ones on each board. These resistors warm up the incandescent bulbs for the flashers so that they can flash on and off quickly. However with LEDs, the resistor being on there will cause flashers to stay on or act funny because its supplying small current to it and LEDs dont need much current to illuminate, so they need to be removed. You can always desolder one leg if you want. But you definitly dont have to put it back if theres and LED there.

#3 definitely sounds like a tilt. Play it tonight. Pull the glass off and try holding down both flipper buttons and touch every target on game and every wire switch including any ball gates. Put your hip one flipper button and hand on the other and hit every switch/target on the playflied. Its a easy way to load test it and isolate the problem. if it resets, you have a bad diode under the playfield tripping the tilt circuit causing this "reset".

Mine did the same thing and it was a bad diode on the flipper switch. See pic

339963F4-6A6C-4720-AAEC-A5BD947626ED (resized).jpeg

ahhh, I see now. Says it right in the schematics, cant go below 10.5v or you get intermittent reset ...

f14 (resized).png