Today I logged in to play and I had 1 weapon unlock. I choose FELINE. The n I played a bit, leveled up and won another unlock. I went to the class customization, and suprise. FELINE was locked again and I had no weapon unlocks

Now I have 1 module unlock for FELINE, but I can't spend it , cuz the gun is locked (I can use it, though; I choose it for one of my custom classes, but if I change it to another weapon, I won't be able to get it back. I'll have to get ANOTHER gun unlock)

So, WHY the game keeps on stealing my gun/dog tag unlocks?
How many levels I need to get one gun unlock?

Also, how do I change my ingame nickname?