That's exactly what's happening but I doubt there is a defect in the chamber.
As mentioned, the tolerances on most Baikals is tight and that is an understatement. Great shotguns but they have to much drop in the comb for most people, so felt recoil is horrendous on both SxS and SS guns.
The last Baikal SxS I had was sold because of the issues the OP has.
What I found was the chambers are also tight, right on minimum spec. The case heads are jammed back against the receiver face and cause opening to be very stiff after firing. IMHO, the metal shell heads are expanding and slightly stretching back against the breech block face and this is what's causing most of your tight opening issues.
OP, the next time you put a loaded cartridge into the chamber take a bit of notice at how tight the chamber is. On my last shotgun, the shells wouldn't slide into the chamber by gravity alone, they had to be given a bit of a push to seat them all the way onto the ejector.
