Jim, the Hawke Sidewinders and TAC30's that i have had (some bought years ago and two recently) are all good. Not too sure about the first one you had, but the second one sounds as if the screw on top of the turret needs nipping up. The screw is designed to be loosened so you can reset the zero once dialled in.
If you are unsure, speak to the importers, Deben, they are a helpful bunch and will get you on track either with advice on how to put it right or with a fix of the issue.
Hope you get it sorted as the scopes do offer a lot of bang for your bucks and IMO the best reticles out there.