Please be aware that I have tried extensively to replicate this bug outside of combat but cannot. However, whenever I am in combat and use Shotguns, sometimes C4 or any weapon requiring the fire button to be spammed while moving, the game alt-tabs even when in full window mode (my default is usually window fullscreen). As a result the game is unplayable when using shotguns. I have managed to narrow it down to the forward and/or back motion since it doesn't happen when you attempt to strafe using the left or right movement keys. or if shooting when stationary. For what it's worth I use default mapped keys (WASD + LMB). The Alt-Tab occurs immediately upon pressing fire so you will fire and then be stood there while you have to click back into game. I've been playing this game since its release and this bug has only begun this calendar year.
