Sighted in my encore 12" 44 mag last week. Shot it again today and it is dead on but 4" low at same distance. Am certain the gun has not been knocked off. Did my red dot move forward or backward in the rings?

Get a sharpie and make a mark on the scope tube. Make the mark on the rearward part so you can see if the line moves back. Are you shooting using the same rest and technique?

I use white out instead. And cake it on to the back of either ring or to the front. If the scope moves it will break the white out. It's easy to see and to remove and doesn't leave a permanent mark.

Under recoil the gun moves back / scope moves forward.
Clean scope tube and rings with alcohol before assembly

Did you use Loctite?