now let me explain to you how this works so u have a better understanding as to why.
1) ur rubber trackball is like a car tire, it will wear out eventually. when it gets "bald" thats when its not gripping the teeth/rail. (this cannot be fixed, a replacement is due)
2)ur trackball is like a mouse that we used to use with a ball at the bottom. it has 4 straight bars with teeth holding that ball in place, when you roll it, it makes the bar rolls, hence the rolling movement. it will get dirty time to time, and it does require cleaning when it gets "STUCK" and are not moving into one direction. although reasons may varies as to ur trackball functionality, but dirtiness is the main reason why.
cleaning it - you may use nail polish remover, or any alcohol to rub it with a cotton swap lightly, make sure ur phone is OFF, and not too wet. then just clean it thoroughly. then, make sure it is completely dry before u ON ur phone.
just simply replace it - you can order here for RM30 for free installation for any colors you like! =D
CLICK IS SOFTER, NON-RESPONSIVE
so, when you press on this ball from the top, something at the bottom, thats attached to the motherboard module, called a TRACKBALL DOME, its a very thin piece of metal thats shaped like a dome, pushes it back up. over a period of time, due to over usage, it loses its functionality, and it needs to be replaced. hence, the "softer'' click.
or that water/sweat somehow got in between it, and make it not touching the motherboard module when u click, a cleaning is due.
SO FAR, AS I KNOW, there is nowhere in malaysia that offer this service, if they do, they will easily charge you 50-100RM, cuz this part is hard to come by, and it requires to take apart ur phone completely to do. i can replace it for you for RM30 =D