There’s one modern make of piano where the rail holding the strip of felt operated by the middle pedal has an annoying habit of flipping upside down so that it can’t function. Once in that position, the only way to reset it is to open up the top of the piano and reach inside.
However, the strategic placing of a simple screw, as shown, completely solves the problem as it prevents the rail from flipping.
I commend this solution to all owners of Wendl & Lung pianos, and to the makers too. I’ve had to do this to at least 3 instruments of this make of piano (screw in top RH corner of picture).