Going through each map, I noticed on Bridge that the EV goes through the animation of blowing up HQ but it still requires you to stay an extra 2 seconds for it to register that the EV objective is finished.
When this happens and a player opts not to stick around for those 2 seconds, players will be able to enter HQ but not find any datacores.
Also I imagine this bug has been reported already, but I cbfed searching for it. 