Took the GSG5 out of the safe today. Ran a couple mags through with no issues. Then it failed to fire. Attempt to pull the bolt back and it gets about half way back and stops. It ejected the spent round and loaded a fresh round but did not cock. The bolt retracts enough to let the next round out until just the case is out of the chamber but the bullet is still in so I cannot remove that round. Any thoughts as to the way forward?