mijo, I very much doubt your hypothesis, if you're implying that there is magnetic pull between the amplifier power transformer and the cantilever. Transformers do generate EMI (electro-magnetic interference) but not very much magnetism. And cantilevers are not ferrous. Could EMI from the amplifier be degrading the sound? Yes, and maybe that is what you meant. If so, sorry. EMI usually causes problems by feeding back into the AC supply at the wall outlet. Try plugging the amplifier into a different outlet, if it is now sharing with the turntable and/or phono stage.
Seems there are possibly two issues which may or may not be related. The cantilever is not straight, but it was not straight for a long time before the sound went bad. Possibly it bent past some critical angle and now is hopelessly out of line with the internal generator of the cartridge, or possibly EMI from the nearby amplifier (or some other undiscovered source of interference) is the culprit. But anyway, the cartridge is now broken, is it not?
Seems there are possibly two issues which may or may not be related. The cantilever is not straight, but it was not straight for a long time before the sound went bad. Possibly it bent past some critical angle and now is hopelessly out of line with the internal generator of the cartridge, or possibly EMI from the nearby amplifier (or some other undiscovered source of interference) is the culprit. But anyway, the cartridge is now broken, is it not?