Make sure the bridge diverter works every time.

I suggest inspecting the shooter lane very thoroughly as it can tell the entire story of the machines history and how much use it had , good shooter lane = buy , because all components are likely in good condition , bad shooter lane , means very roughly abused and man handled . Kind of like a if the steering wheel on a car is very worn it means driven hard and likely never changed oil at 5K or better intervals

Look for playfield wear in front of the rocket which is common and can usually be covered by a Cliffy. Also the clock is a well known failure point due to heat from incandescent lamps. Enter test mode to see what problems are listed, will say clock is broken.

https://pinside.com/pinball/forum/topic/twilight-zone-what-to-look-for

Make sure clock works and powerball registers in trough and subway

opto's, and opto's make sure all work