This was exactly the case. The gear box is a bit loose so the flipper doesn't fold deep enough every time to engage the limit switch and the cycle stops.
I guess there are no new gearboxes available so what would be the best solution for this problem?
Could the limit switch button be made a bit longer or have some extra padding on the flipper to the point which should hit the limit switch? It's not much what's missing, about 6 millimeters (0.24") that causes the problem.