One of "Your" air rifles..

[Talon]

I've had this problem with worn out bsa meteors but not with a Weihrauch. It does sound like a lockup issue though Mort.Have you tried easing off the tension on the barrel bolt.Im guessing you're losing zero vertically?. I would ease off the barrel lock up bolt a little and try again . It may be too tight . I know it sounds strange but it may help.
If that doesn't work you could try adding weight at the muzzle to see if that cures it. The HW95 can suffer from muzzle flip and weighting the barrel can cure it. I've not heard of it happening with the 30 but that's worth a try too.
If neither of those suggestions help it may be a fault with the lockup itself, or the scope mounts . I can't see it being six faulty scopes though.
Are you using the same mounts with each scope Mort?. I always use a quality one piece mount on Spring rifles. I'm not a fan of two piece mounts even with a stop pin.