The reason is probably dust which has accumulated below the scroll wheel.
You can unscrew the mouse remove the wheel and clean it with alcohol or something similar.
Of course getting a new mouse in another option. :P"
how can I download old AR3 and AR4 files *Arplant.I bought full version just now. Still looking for stunningplants and bushes of old version.Please anyone send me the link or downloadable files on my registered email.See More