I noticed the same thing, carrier was slightly off center to the machined receiver slot, and positioned to the right, looking at it from the bottom and it's a RH gun. I was a little concerned at first, as the first round I tried to load into the mag didn't go in and jammed, but I think that was bolt wasn't completely seated against the barrel (first time with auto gun w/mag probably my mistake because all the rest I loaded into the mag loaded fine.). I just fired (last week) about 60 rounds through my new SBEII and it performed flawlessly with a variety of shells. Quality 3.5" shells dropped about ten+ feet away, quality 3" landed six+ feet away, and the cheapest of cheap 2.75's, 1 1/8 load, barely made it off the ejector landed next to me; but still ejected....
Overall I was pleased with my gun and in your case I would clean the heck out of the gun and lube it, wipe ALL excess oil of the EVERYTHING, then give it another performance go.
I wonder if it's designed into the the function of the gun and if you have a RH shell carrier installed on a LH gun. Possibly the carrier is designed to be slightly off center and promote shell loading....It's a reach, but it just may be a factor....I wouldn't expect it to be crucial to loading, but you never know....
Do the shells eject well?
Kevin