Parallax knob - Vortex Viper HS 4-16x44mm Rifle Scope, 30mm Tube, Second Focal Plane

The glass of the scope is of good quality, but the settings and in particular the parallax setting, turns very difficult to the extent that it sometimes hurts my fingers and I have to take my head away from the rifle stock so as to use enough force to turn the knob. The parallax knob is in comparison with other scopes, not as smooth when adjusting. I do not know if it can be lubricated.

I also have an older 2.5 x 10 Viper HS. The rubber near the objective lens with which the magnification settings are turned, is loose and did not last long. (The rubber is glued to the tube) It is difficult to turn the magnification up or down and the rubber forms a bubble. The turning to another magnification is not smooth and requires an effort. It however seems as if the newer models do not have this problem as they do not have the same rubber.