I believe you hit upon the problem in your last post. When I bought my 10/22it had a Ramline plastic stock and (ironically) the Ramline 30 round mags did not work very well. They just didn't seem to lock up properly and I had constant issues with misfeeding. Later, I replaced the stock with a Choate synthetic stock haven't had any issues with magazines since.
I realize that one more rifle isn't much of a sample group, but you may be on to something with the stock.
NRA Life Member, SAF contributor.