Over the years I've seen dozens of these on as many shotguns but they rarely seem to remain tight. This is more than a little predictable. They are made of the same extruded aluminum alloy as the usual see thru rifle mounts. Another wild card is that most of the shotguns to which they are attached do not have a solid connection between the barrel and the receiver. So even if the saddle mount didn't flex and shift with every shot the barrel is free to wiggle just a little with each shot. No doubt the problem is compounded by cheap scopes and hard butt plates. It is the rare slug hunter who spends more than $50 on his scope or any money at all to soften the recoil of his 12 gauge deer gun, which when loaded with slugs, kicks as much as a 375 Holland and Holland Magnum (yes, an "elephant gun").
There also seems to be a tendency on the part of the frugal deer hunter either to buy whichever brand of shotgun slugs are cheapest, or to buy only a couple packets of the very expensive premium jobs ($3-4 a shot!) but then not practice very much. Some shotguns come with two interchangeable barrels, a choked smoothbore for birds, and a shorter one - some smooth, others rifled - fitted with with open sights for deer season. There has been more than one occasion when, frustrated by loose mounts or an optic that won't hold its zero, the hunter finds he shoots better with the open iron sights.
There are some better choices for the hunter who prefers a scope or optical sight. There are shotguns with barrels that fit very closely in the receiver. There are shotguns with receivers drilled and tapped to accept a scope base. The best solution is probably those guns that allow you to attach the scope directly to the barrel. FWIW, I have also noticed that teenage girls shoot their lighter kicking 20 gauge guns better than their brothers do Dad's 12 gauge; go figure.
There is no shortcut to skill at arms, especially with slug guns. Buy rugged, simple gear and practice, practice, practice.