OK, If the rifle is still doing this, these are the things I would check/do first:
1) Detail strip the bolt, clean out every remnant of packing grease, then oil the ejector spring and extractor spring with a good gun oil. Leave the firing pin channel bone dry - no oil at all. Reassemble.
2) Get some lubriplate or SuperLube from the hardware store. IMHO these are the best M14 greases around. Some guys get good results from wheel bearing grease or white lithium grease. I've used wheel bearing on my oprod springs, but for inside the receiver, use one of the other choices. If you get white lithium, do not use the aerosol one - get the stuff in a tub or tube.
3) Heavily grease the inside of the oprod hump, the bolt roller, the top and bottom of the bolt lugs, the bolt lug raceways inside the receiver, the inside of the receiver heel and any surface the bolt slides against EXCEPT the parts of the lugs that lock into the receiver - leave those contact surfaces dry.
4) Heavily grease the oprod tab track and the side of the receiver ring where the oprod rubs it, and also on the oprod ledge beside to oprod tab track.
5) Rub grease all over your operating rod spring and lightly grease the part of the oprod that slides on the operating rod guide (the thing attached to the barrel the oprod rides in).
6) Run your gas system DRY.
Now re-assemble everythign and when putting in the trigger group, make sure the dished out part of the hammer that the bolt rides over is greased too. Yuo can also lightly grease the hammer hooks.
Should solve your problem.