You guys have a classic case of mis-indexing of the barrel. What that means is when the barrel nut was screwed onto the upper receiver, the barrel rotated slightly as the nut was tightened. The front sight was basically moved to the left.
When you adjust the front sight, you move it in the opposite direction you want the bullet to go. When the front sight was moved to the left, as the barrel nut was tightened, it created excessive right windage. In order to get the rifle sighted in, you needed to move the rear sight left.
If you have a barrel nut wrench, and an action block, you can fix the problem quite easily. If you don't have the tools, get a hold of the manufacturer, and see if they will fix it.
I believe the twisting movement of the rear sight is normal. I like the A-1 sight, because of its simpler, no bling operation.