The game reports the clock is broken.

Twilight Zone: "clock is broken" error

Cause: Heat from the #86 GI lamps inside the clock cooks the U slot optos, their 470 ohm feed resistors and the .100 inch connector between the two clock boards.

Checks

• Inspect the clock boards for burnt traces, failed optos, burnt R1-R8 and cold joints on the interboard connector.

Fix

• Replace all the U optos, resistors R1-R8 (470 ohm 1/2 W) and the .100 inch interboard connector.
• Reduce the heat with one of the clock lamp mods (LEDs, or diodes in series with the #86 lamps).

Systems

• WPC Fliptronics

Games

• Twilight Zone

Related tips

• Twilight Zone clock uses eight sensitive U optos
• Twilight Zone: diode mod to cool the clock with stock bulbs
• Dark MPU LED: follow +12 V through R29 and Q2
• Four-leg U optos need the high-sensitivity grade
• Twilight Zone: adding an adjustment pot to the trough proximity sensor
• Twilight Zone trough proximity sensor (switch 26) problems
• Twilight Zone ninth switch column (clock switches)
• Test report lists switches the game doesn't have

Source: Repairing Williams/Bally WPC Pinball Games from 1990 to 1999, Part Three, Clay Harrell (pinrepair.com)