Every shot up the left ramp ends the ball as if it had drained. It looked like a shorted switch diode in the matrix.

Phantom drain on every left ramp shot: two wires fused inside heat-shrink

Cause: Two wires running together inside a heavy heat-shrink sleeve (under the upper playfield, over a plastic and down beside the upper drop targets) had melted together and shorted, though the outside of the sleeve looked fine.

Checks

• In switch test, see which switches close together when the ramp switch is hit.
• Follow the wiring for those switches and open up any bundled or sleeved sections, especially where they pass lamps or bend over plastics.

Fix

• Separate and repair the fused wires (or replace them) and re-insulate them, routed clear of heat and sharp bends.

Systems

• Data East/Sega CPU Version 3b

Games

• WWF Royal Rumble

Related tips

• One switch fires something unrelated (phantom closures)
• What a bad switch diode does
• Which switches are outside the switch matrix
• Use a real ball in the switch test
• Test a leaf switch diode in place
• Check the switch matrix with a logic probe
• Resistor networks in the switch matrix
• Test a switch diode (fail-safe method)

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