Touch Sensitivity Problem

by Alex

i have a yamaha ypt-310 and ive had it for many years and over time ive noticed certain keys will not play to touch such as if im playing very lightly on a specific F# key it will play F# but as loud as if i didnt have touch on at all and the opposite is true for other keys in which i press at normal pressure or hard and a certain key will play it soft, lastly sometimes instead of playing too hard or too soft it wont play it at all, which as you can imagine is frustrating. like i said ive had this for quite a quite a few years and its a wonderful keyboard that brought a lot of entertainment but i was wondering if i can fix it, or is it just because its getting old from my constant use? Thank you for reading this