I have noticed this too, but only since I installed easy mode. Have you done that too? Been playing for a couple years without trouble in factory default mode, but have never been good enough to make it through all the modes and through all of Sea of Simulation, so I finally caved and tweaked the difficulty level down. And that's when I experienced the weird flipper dying phenomenon. Just like you describe, as if a tilt occurred but without reason to. Game resumes fine after losing the ball.

I might have to sell the game soon and so I have less than my lifetime to try and beat it, was hoping to achieve that through easy mode. I will eventually restore factory defaults if this bug persists (and stymies my efforts to make it through to the end of the game -- almost like the coders are laughing at us!).

Made it Portal finally, yay, and have had no recurrence of this flipper issue since my previous comment. Will be going back to factory defaults now anyway...

The problem lingered for me, but was just balls ending unexpectedly. I figured it had to be a trough issue -- switches or optos, and indeed saw on Marco Specialties their notes about Stern trough optos failing with symptoms like this. I ordered and installed a dual opto replacement kit and all appears to be well now. I recommend the OP try the same.

Good to know. I did suspect loose connectors, and did fiddle with them a bit, but perhaps could have tried harder to solidify the connections. Might still give that another try to know if I have spare working optos, thanks.