I have a Umarex scope mounted on a pretty violent Umarex Octane (it came with the gun). Reticles and focus are very clear. Ive tried everything to get it zeroed, shims, new scope rings etc. A week ago it was dead-on at 25 yards, now the adjustments make very little change in POI, and I run out of adjustment for left /right, up/ down. Is the scope DONE?