I would start with the 3" flippers. The coil sleeves look old and discolored and it appears there might be a bit of rust or pitting on the plungers. I would just replace the coil sleeves and take some steel wool to the plunger surfaces. New sleeves will often make a small, but noticable difference. Also make sure that the End-of-Stroke switches do not open until the last couple mm. Might also back the return spring off by 1/3 revolution and see if the flippers still return cleanly to the rest position.