Good scope; however… - Vortex OPMOD Strike Eagle 1-8x24mm Rifle Scope, 30mm Tube, Second Focal Plane (SFP)

This is the second scope of this brand & model that I purchased, this one to be mounted on my T/C Contender in .223. It mounted easily. I focused the reticle with the focus ring until the reticle was clear and sharp. Yesterday, zeroed the scope to the capabilities of the barrel - under a half inch at 25 yards. Went to shoot at 50 yds & 100 yds, the target was so out of focus that I couldn’t see the target lines! Readjusted the bell focus to correct; but then I couldn’t see the 25 yd target.
The exact same scope on my other rifle doesn’t have this problem - it’s in focus from close to infinity.
So, it looks like I have a defective product. Now I’ll see how just how good is the warranty on this scope.
I’ll review once again with my attempts.