There are a number of common causes for weak flippers. However, you report the pop bumpers are similarly weak?

Do the slingshots seem weak also?
If so, the issue is most likely a voltage drop across a switch along the right side vertical buss on the schematic.

I doubt any serious owner would intentionally lower the power to the pop bumpers in order to prevent the ball from cycling between the right most bumper and the kick-out hole, but strange people are out there. The proper fix would be to adjust the kick-out trajectory by bending the kicker arm slightly so that the ball is not launched directly at the pop bumper , thus causing it to rebound back at the hole. Would only require a 0.5 mm adjustment to fix that issue.