do not use steel wool on the mouthpiece shank or inside the receiver. You may change the shape/contour so that a mouthpiece will not seat properly. Also, removing the silver plating on the mouthpiece will make the two brasses of the mouthpiece and receiver will make them more likely to stick or fuse together.

This is not a corrosion over time problem. It is from being dropped or some other kind of forced pressure. Just putting a mouthpiece in without a gentle twist will cause them to get stuck too.

Not a gunk/corrosion problem with a mouthpiece, tuning slides, yes, mouthpiece no.