Nothing wrong with the game.
This is what happens to all system 11B and 11C games (with the Aux driver board) when you install LED flashlamps into solenoid spots 3,4, 6 and 7.
There are tie-back diodes on the large TIP36 transistors that connect those circuits to the 50V power source. There is a some feedback into these circuits from the flippers that is not apparent until you install LED's.
To fix this, Cut diodes D3, D4, D6 and D7 from the aux driver board. Then add diodes onto the coils for solenoids 3,4,6 and 7 (banded end of the diode goes to the power wire)