I was just reading the matrix diagram for that game and if you already checked for missaligned board plugs its possible that somebody repinned the green wires and they could have gotten the grn-brn and grn-red wires transposed. If so you could get the exact effect as the jet bumpers would trigger as credit, credit and slam tilt. With a game running trigger top roll over A and the Outhole, if either triggers a tilt warning or tilt while the actuall tilt mechs trigger scores then start checking for the transposed or shorted grn-brn grn-red wires.