Some thoughts.

When it's stuck up, turn the game off. If it doesn't you have a mechanical issue. Plunger in coil sleeve, up and down play so pawl isn't binding on the nylon bushing the flipper shaft rides in.

If it drops, then electrical issue. I'd start by removing the plastic flipper button from the cabinet and clean with 409, windex, etc. Rinse and then dry good. Put it back in. see if the flipper button sticking was your issue. ( they get gummed up from hands - dirt, sweat, etc. )

LTG : )

I bet you it's the flipper stop, I had the same problem, the back stop block got loose and interfered with the flipper (the "L" shaped bracket at the end of the coil"), you'll have to change it, call Stern and ask them to send you a new one.

s-l500 (resized).jpg

If it's new, and you're having this many issues, shouldn't Stern/distributor be assisting? Or is it just new to you? Or am I, being new to the hobby, simply naive?

I'd loosen the flipper bat and move the flipper up and down a few times, then retighten it down. It may be binding..just fixed similar issue on a customer's lotr and tspp.

From underneath, move the flipper mechanism back and forth, does it bind at all or seem to stick? If so, do what I stated above.

It might be something simple like the flipper is not clamped tight enough. First thing is to do what LTG says and determine if electrical or mechanical. My left flipper was getting sticky on my MET pro. Tried several things but ended up only needing to be taking apart and cleaned.