Honestly the preferred weapon system has been screwed up from launch. The last patch hinted at a repair, but it does not seem to be the case. Your best bet is to just give it time and the issue should be resolved for you me and everyone else effected. Hope that helps.
I noticed that the Ghosts App lists my preferred weapon correctly, but in game doesn't. You'd think that the app would be pulling the data from the same source as the game, but the game still lists a weapon that I've only used once or twice when it was a default starting gun.