Hello.
2 fix not saved data:

All the data, as Rank, Perks etc Saved on SERVER side.
So - saving will work seems only being CONNECTED to Server.
Means You MUST be logged in to some ranked game - and in between the battles make all the settings in
Weapons and then press Leave Session.
Then You see promt Updating account Data.
Thats the moment of storing data on server.
If you make dome changes being NOT logged on - at quit you'll se nothing - game just quits


Please check that. Worked for me.

Stats are ONLY saved when u leave a session.
Which means: when you have unlocked some attachments or leveling up, you should leave the session.
ONLY then it will be saved.
Actually it even isnt a bug. Just serverside-programming fail.