That sounds like a combination of possible problems. A dirty/partially plugged gas port and a dirty extractor spring. Either would contribute to that problem. Get a bolt tool and take down the bolt. Carefully remove the extractor/extractor plunger and extractor spring and clean them thoroughly as well as the hole the spring and plunger go into. Chances are, that will be enough to resolve that issue. Carbines can be sensitive to built up crude in the extractor system. And while you have the bolt apart, it would be a good idea to clean out the firing pin channel too. Crude can build up at the front of the hole and "cushion" the firing pin strike against the primer.