Your cartridge is 25+ years old. Sounds like it might be time for a new cartridge! The suspension elements of a phono cartridge will not last forever, as the rubber suspension parts will decay. This can occur even if the cartridge has not been used very heavily.
Also, do you have a sturdy table stand, and have you changed the TT stand recently?
Also, do you have a sturdy table stand, and have you changed the TT stand recently?