I'd have CDNN sports check that rifle out very carefully. Not beyond the realm of possibility they swapped some parts out. Also not beyond the realm of possibility they screwed up the rifle while swapping the parts out. Sounds like they are stalling to me. This may be fraud.

A whole lot of instances of ordered rifles being returned for any old reason and having swapped or broken parts in them.

I always use the local Rod and Gun Club as an FFL.

They sure have changed the system since I've been in. Used to be you took your receipt, registered the rifle (or handgun), returned with your registration card and picked up your rifle or handgun.