The game reboots part way through booting, and reboots when the flipper buttons are pressed, even though the 5 V test point on the driver board reads close to 5 V.

Reboots at start-up and when flipping: flaky power connector to the CPU

Cause: A poor connection in the power cable between the power driver board and the CPU board, so the CPU sees a lower or dropping 5 V.

Checks

• Compare the 5 V at the driver board test point with the 5 V on the CPU board (for example at the game ROM's supply pin or a filter capacitor); more than about a tenth of a volt lower at the CPU points to the connection.
• A meter can miss brief dropouts, so a steady reading does not rule out the supply.
• Make sure the board mounting screws are tight, since they carry ground.

Fix

• Replace the faulty connector or cable between the driver and CPU boards (here, swapping in a good one from another game cured it).

Systems

• WPC Fliptronics

Games

• Bram Stoker's Dracula

Related tips

• Reading the CPU board LEDs at power-on
• Resets during the Powerball battle: reseat J101 and J115 on the power driver
• Resets: +5 V at the driver board test point is low
• WPC-89 resets on low +5 V: replace the small 100 uF 5 V filter caps
• WPC CPU board LEDs at power-on
• Switch rows 1-3 show shorted to ground: opto board missing its column strobe
• CPU diagnostic LED blinks a code instead of flashing steadily
• After a power cut: resets, then won't serve a ball

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