Assuming you've already done everything mentioned above (eg re-pin and fuse holder checks, etc)...
Try looking at the flipper driver board. They're normally mounted in the bottom left of the cabinet under the playfield on DE machines... Re-seat connectors, then when that doesn't work, reflow, check the IC legs are good (they're not if black or rusted), check the transistors on it (may well be one of these failing under load). See page 2 of the manual (6 of 93 on the IPDB pdf for the location and page 64 [87 & 88 of the pdf] for the circuit diagram).
Try looking at the flipper driver board. They're normally mounted in the bottom left of the cabinet under the playfield on DE machines... Re-seat connectors, then when that doesn't work, reflow, check the IC legs are good (they're not if black or rusted), check the transistors on it (may well be one of these failing under load). See page 2 of the manual (6 of 93 on the IPDB pdf for the location and page 64 [87 & 88 of the pdf] for the circuit diagram).