The game keeps resetting over and over, and digit 16 is missing on the player 1 and player 3 displays.

Gottlieb System 80A: constant resets and digit 16 missing: shorted 7404 at Z26

Cause: The 7404 at Z26 was shorted on pin 8, which also triggered the reset circuit.

Checks

• When resets come with a missing display digit, probe the chips that drive that digit's strobe for a stuck or shorted output.

Fix

• Replace the 7404 at Z26.

Systems

• Gottlieb System 80A

Related tips

• How System 80A differs from System 80
• System 80 and 80A CPU boards swap only with the matching U2/U3
• Swapping CPU boards between System 80, 80A and 80B
• Same digit wrong on the player 1 and 3 displays: failed Z17 on the MPU

Source: Pinball Repair help group!! (Facebook group)