Ground row short Row 1 indicates something in row 1 is (you guessed it) grounding out! The row #1 switch are:
11 - Launch button
21 - Slam Tilt
31 - Trough Eject
41 - Not Used
51 - Left Slingshot
61 - Left Low Loop
71 - Right Ramp Enter
81 - Up/Down Bank Up
I'd check the Slam Tilt first.