Flippers seem dead, weak, or report a bad EOS switch, and the flipper opto boards seem to be at fault.

Weak or dead flippers from failing LM339s on the Fliptronics board

Cause: Failed or leaky LM339 comparators U4 and U6 on the Fliptronics II board (Fliptronics through WPC-S). On WPC-95 these chips are on the CPU board at U25 and U26.

Checks

• Swap the two flipper opto boards. If the fault does not move, suspect the LM339 chips.

Fix

• Replace the LM339 chips (socket them).

Systems

• WPC Fliptronics
• WPC DCS
• WPC-Security (WPC-S)
• WPC-95

Related tips

• Two LM339s on the Fliptronics board read the flipper optos
• Fliptronics and WPC-95: weak flipper
• Fliptronics: flipper coil gets hot after a while of play
• Flipper gets weaker the longer the game is on
• Row or column "ground short" errors
• Optos test good but still don't work: the opto board
• "Check Fuse F114/F115" (F106/F101 on WPC-95): step-by-step
• A dedicated (direct) switch does not work

Source: Repairing Williams/Bally WPC Pinball Games from 1990 to 1999, Part Three, Clay Harrell (pinrepair.com)