Slider problem

Hi ppl,

I have a problem with my mixer that's already been going on for a while, but it's getting worse.  The sliders of my faders and the rotary buttons produce noise when manipulating them.  Also, somethimes the left channel fades out a bit by itself.  The origin of that problem is rather unknown, because it occurs when I use the bass frequency rotary and the crossfader (and maybe even the fader from the channel itself, but I'm not sure about that). I once fixed the crossfader problem with compressed air, but the noise was back again rather quickly. but the rotary problem is rather new.  Is my mixer wearing out?  And should i buy a new one? It's an IMG Stageline (daughter company of Monacor), and rather budget, so that probably contributes to the problem as well.  I have it for about four or five years now.  And it's been used regularly (about once a week).  I don't know the type exactly, but I can look it up and post it here later, if it should help. Any ideas?  Thx a lot in advance!