The caps are usually to stop arcing, so should not impact on flipper strength. If it is just the top flipper, and not the coil stop, the most likely culprit is the switch that feeds the top flipper (the switch outside the EOS that is pushed shut when the bottom flipper on the same side closes). Also check the EOS on the top flipper and file or replace if the points are badly pitted.
+1
Will be the advanced EOS on the lower flipper (not giving enough power), or the EOS on the upper flipper (hold) needs a clean or adjustment.
