When the bolt does not initially lock up completely, the FP can not fully protrude out the bolt face, and most of the hammer contact to the firing pins is just driving the carrier forward to lock the bolt up; with not enough FP initial force to the primer once it reached it to ignite it.
If flip the B/C over with it in hand, pull the bolt forward like it not fully locked up, you will see that the tail of the bolt is not protruding out the back of the carrier, and why this fail safe happens (so the rifle will not fire when the bolt is out of battery).
Normally when this happens (bolt not fully locked up) you should be able extract the unfired case with not problems (making sure that the bullet came out with the case, and not still embedded in the bore to case a KB if another round is loaded and fired with a second bullet obstructed bore)
The fact that is a bitch to cycle the live unfired round out is screaming of one of two problems.
The first, is that the gas tube is not correctly aligned with the carrier key.
To check this, remove the bolt from the carrier and dry fit the carrier to the upper receiver. The sides of the key should not drag on the sides of the receiver, and about an inch before the front of the carrier touches, the back of the barrel extension, the gas tube should cleanly enter the carrier key. If the gas tube is binding when entering the carrier key, pull the hand guards off the barrel and tweak the gas tube over the center of the barrel to get to align correctly with the carrier key.
The second, is often the failure to clean the rig correctly, and could be either a sluggish fouled action, or just too much crap in the chamber from not scrubbing the chamber with CLP by hand with a chamber brush. Here, it really breaks down to not only correctly cleaning the rig with the correct solvents (CLP mostly, with the exception of the bore that takes a good copper solvent like Sweets instead), and then making sure to lube the upper receiver bearing areas with CLP as well.
Note, if you are shooting steel case ammo, scrubbing the chamber every cleaning, and running the upper more the wetter side with CLP will go a long way between problems/rifle starting to foul choke out and need to be correctly cleaned again.