The "jamming" has to be a bug. I never see it happen to me, although there was a game wherein whenever I picked up the Bowcastor it would be stuck in the "zoomed in" animation, but without the scope! That was weird. Dropping it didn't seem to fix.
I guess there were times when I had the shotgun and it was stuck partway through the "reloading" animation, but it seemed to work fine, the model just looked weird like that.