Round not chambering. Won't extract either. HELP

I have a CBC upper with about 200 rounds through it. Functions almost flawless but on a couple of ccasions a failure to feed. The bullet looks likes it’s chambered but it’s not fully closed. It takes all my might to pull charging handle back and it doesn’t extract. I have to use a cleaning rod to stick through from muzzle to force the round out. Only issue. Does anyone know what would cause that?

Call a gunsmith and ask. It could be the head space or the barrel is not torqued down properly and allowing it to shift enough to cause the rounds to jam. I had this happen on a brand new upper, very first round. I put the upper in a freezer for 15 minutes and then yanking the charging handle as hard as I could, the round came out the second try. The case was all torn and chewed on the lip. The barrel nut was never torqued at the factory. I could shake the whole upper and feel the movement. Call Brownells and ask a gunsmith. They will be happy to help.

Thanks for the reply. It fires most rounds without fail but just once and again it does this. I have noticed it only happens with hand loads