Even if you have the option “full screen” if you reduce the resolution below the resolution of your monitor the game will be in window mode.
Occurs sometimes when you are loading your weapon, you accidentally drop the ammunition magazine removed.
Although empty, the 5,56 drum still displays the bullets.
By some chance the single player mode has a much lower fps than on the servers, I detailed more about that below.
Anyone aware of any other bugs feel free to share them here.