sigma lens issue

[smithey1981]

Since buying a sigma 18-50 2.8 last year I have always not been a 100% happy with the af. However recently it seems so hit and miss especially from 30 to 50mm range. I have had it on 3 bodies and it is the same on all 3. Any suggestions on what to do I doubt having a repair is an option due to the price I could pick another one up for

 

[Nikon_Nick]

Is it not still under warranty?

 

[smithey1981]

Unfortunetly i brought it second hand off here should have contacted the seller when i noticed

 

[holty]

maybe dirty contacts on lens or camera ??