Why my Amp makes a crackling/static sound when turning the volume knob? ('Fender Mustang III')

My amp has been safely unplugged in a well temperature & humidified bedroom for the past 6 years. It's only been played about five times ever & I always keep the dust off of it. After years of safely sitting, i powered it up, and noticed when I turn the volume knob there was a static/crackling noise. I read it can be a dirty potentiometer, which I should clean.; so I used a 'Wd-40 Contact Cleaner' spray on the knob from the outside (Has a couple little slits).I didn't take apart the amp to clean inside b/c I don't know anything about electronics. I think it improved a little, But just in case, Is there anything else that can cause the Staticky-Sound When Turning the a specific knob?