I have seen very similar symptoms in 700's stuck ejectors. It may be a good idea to make sure the ejector is right.Before you buy new parts, you could remove the ejector and then try it in the gun. That way you remove one more item from the list of possible reasons for the failure.
I'm still working on this one: I just picked this rifle up in a trade. The ejector is very strong. The case comes out of the chamber. The case then falls back into the action. I've not had this happen with my 700's. Bubba may have worked on this extractor. There is no mark on a case head of the ejector rubbing. It's not a jammed ejector. OP's extractor would not had a rivet.The Extractors on the Remington 788s were the weakest point of the rifle.