Dose this game have regular flipper button switch's, or optic's?

Ok left switch's, how do the contacts look?

By your description it sound like maybe the pull side of the coil might be bad.

I would pull the flipper board and inspect, how do the connecter's to it look?

How does the flipper work if you jump the coil to ground braid ?
To me, it sounds like you flipper board isn't getting a good ground, causing intermittent and weak flips
and not providing a complete path for the coil.