Will not stay sighted in - Weaver Kaspa 3-12X44SF ILL Ballistic-X Tactical Rifle Scope

I sent this scope in because it would shoot all over the target. Once dialed in at 50yd. 3/8" group. Setup for 100yd, I set the scope at 12x and set the parallex to 100yd and bullets are hitting all over the target. A 12" spread all over the place. I sent the scope back to Weaver and told them it hits all over the place and not in the same place. They sent it back said it was okay�. I thought maybe it was the barrel. I tried a different scope, it is the Weaver scope that is bad.