Totally possible that ad heat treatment is the problem, but my experience follows:

The mounting technique that might solve the problem {?} I use and have used for many years, and the one we used mounting and boresighting scopes in the gunshop/store is this:

The scope ring is placed on the receiver and grasped firmly. As the nut is being tightened, the ring is jiggled with the other hand in order to help the ring find its own center and seat itself. You can actually feel this occur.

It is easy to tighten a Ruger ring when the ring base is NOT securely seated. This last bit is what I believe causes the lion's share of the problems people say they have with the rings. "Jiggling" the ring and making double sure it is seated prevents the misalignment.

I believe 4seventy is right; misalignment normally causes the problem. The screw is made to be softer than the receiver, and should be. No doubt some may be too soft, but if the ring is merely slapped on the receiver and tightened, without being set into its base, it is very easy to get a "bite" on the screw {clamp} where the screw feels tight but the clamp is only grabbing on the clamp edge. This misalignment I have seen and experienced during the scope mounting process and rectified while mounting. Every time it has occured to me, loosening and jiggling the ring as it is being tightened has solved the problem. As mentioned, I have only had long-term shooting experience with several Rugers, but mounted many in the shop, some on heavy kickers and none that came back goosed-up.

I am guessing that a ring clamp that is really too soft might be a worse offender in the misalignment process because it might feel like it is biting securely when it is not and then naturally later under the stresses of recoil it lets go. Those I've heard of resulted in scattered groups. I'm still having a problem seeing how the POI shift could occur and maintain group size. I have heard of this problem, but never heard of group size remaining tight. I never had one return to the shop where I worked, having only heard of the problem on the internet.

As for misalignment, DoubleD, your first pic looks like it shows a scuff on the ring base on one side. I can't say I remember seeing this before but that might indicate improper seating of the ring and cattywampus pressure under recoil?

Good thread and thanks for posting the pics, too. All this might save somebody else trouble.

As far as you rings are concerned, if it was me, I'd file the burr off, remount using the jiggling technique and I bet the thing won't let go again.

No promises!!