It seems people keep losing either all or some of their unlocks/camos/levels/progress in multiplayer because of this.
The patch notes mention that an issue was addressed which allowed people to gain xp against bots in combat training. Apparently this has been "addressed" already but I'd still suggest not playing this mode for a while.
I'm assuming it's the offline combat training that causes this issue (the one with bots only).
There was just another topic of a poster claiming he lost a few unlocks. He also recalls playing combat training or local multiplayer.
Might not really be the issue but it certainly seems like combat training has something to do with it.