Yep, exactly what you said. I exchanged emails with Remington for a while and asked them if this gun was still safe, they referred me to a smith who I called and he walked me through it.
He had me pull the trigger groups and inspect the top of the receiver for 4 or 5 cuts. I saw them on the closed side of the top of the action, he said they are where the lugs are hitting, and that (just as you said) it wears down the action lugs and that sooner or later the action would stick wide open. However Remy isn't replacing them anymore, they did a decade ago but not now.
The other thing he said was that the dust cover was not critical to the rifles operation but is there for a reason. He recommeded trying to smooth out the marks in the cover groove with a dremil so it's stay in line.
To bad really, this gun is on it's way to the scrap heap.