USB dual Shock Controller!?

i bought a dilong usb 2 shock controller last May 2005. and now the controllers left stick is so hard to trigger specially when you move it left and right. I sprayed it with a WD40 like lubricant but its still the same.

help guys on how to fix this stick to make it smooth again.. If you experience this how did you fix it even with your ps2 controllers. Thanks in advance.

hey guys i'd appreciate some help here thanks.