When I use 'phones and insert the plug fully I get one side very clearly and the other side is very soft. If I mess with the and get a pertial insert, I get enven balance. I have tried blowing it out wht canned air. This happens with al my earphones and earibuds
You probably have a bad earphone jack though one thing that seems to be a general disclaimer for earphone jacks on most/all Sansas is that they’re very tight … are you sure you have the plug pushed in all the way? I was fooled by this with a Sansa Fuze I bought recently. The jack is REALLY tight.
About as sure as can be without having tried with my full strength and it had been fine before and is fine with a partial insert. on the way to the full insert the uncooperative side does give a brief stakic-y sound.