If there is no flash hole in the primer pocket - how does the ignition of the primer push the bullet into the rifling?
If there is no flash hole in the primer pocket - how does the burning powder push the primer cup metal back into the firing pin hole in the bolt?
This thread needed more pictures of the OPs incident.
If powder was so dead the primer didn't ignite it, how did cutting into the case ignite it?
If the primer was hit by the firing pin the cartridge was chambered and the bolt was fully forward/locked.
I can see the bullet not being seated deeply enough and making contact with the lands hard enough to hang up. Had it happen to me, heard of it happening to other people. However, if the bolt pulled off the rim without extracting the cartridge, the cleaning rod should have been able to easily knock the cartridge out of the chamber/off the lands with very little effort. If the bullet did leave the case neck and move forward into the barrel/lands then the case should have extracted easily.
Without pictures, without the opportunity if examine the rifle prior to the gunsmith working on it and based on lack of better description from the OP, it's hard to tell what happened. Sort of like some of those damned accident investigations I used to get dragged into at work. Guess, guess, guess, at what really happened and why.