First they are not loosing contact. If that was the case your bolt handle would acting as a lug. From your pictures I don't see traditional galling where metal is rolled up and there is either a groove or a high spot that causes an opposing groove. I could tell more if it was in my shop but it isn't so this is what I would do. Find a local smith and do a very light lapping of the lugs. And remember grease is your friend. Without it bad stuff can and will happen.