dirty flipper optos??
try cleaning them off.
they are apart of the boards that cover the flipper buttons. you'll see when you push the flipper button(s).
should be 4 of them..total. clean with compressed air or qtip w/ water or windex.
i'd go with the qtip.
(edit) optos are a type of sensors...if dirty can lead to weak or no flipper action.
Great to see you're enjoying Pinside! Did you know Pinside is able to run thanks to donations from our visitors? Please donate to Pinside, support the site and get anext to your username to show for it! Donate to Pinside