I purchased a used lens and the dial just in front of the aperture control (where it has the triangle to mark what aperture number is set) spins freely. The aperture control works and clicks in place fine, but obviously since the indicator dial spins freely, it's difficult to know exactly what aperture number you're on. Is this normal, or is there a way to fix it in place? I can return it to the seller still, but if it's an easy fix, I'll do it myself