The two flashers in the head (the lizard eyes) stay locked on.

Lizard eye flashers locked on, then not flashing: bad drive parts and a missing resistor

Cause: Several faults. The flasher drive transistor had been fitted upside down years earlier, the parts upstream had failed, and the 5 ohm resistor under the playfield on that flasher circuit was missing.

Checks

• Check the drive transistor's orientation and test it, then its pre-driver.
• Check the 7408 gate's output pin for that circuit with a logic probe, and compare it with the same pin on the other 7408s.
• Find every resistor on the flasher circuit on the schematic and check it is fitted.

Fix

• Replace the faulty parts in order (transistor, pre-driver, 7408, and the CPU if the logic still misbehaves), and fit the missing 5 ohm resistor.

Systems

• Williams System 11

Games

• Grand Lizard

Related tips

• Special solenoids dead after fitting an early System 11 CPU in a later game
• How System 11 A/C switched solenoids work
• Which transistor drives the A/C select relay
• Whole groups of coils or all flashers dead: A/C select relay stuck
• Controlled solenoids 9-16
• The six special solenoids (pops, slings, kickbacks)
• Pop bumper or slingshot machine-guns or locks on (Fire! and earlier)
• Special solenoid signal path, chip by chip

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