This is a real strange one. As of the last patch when playing PvP, I notice that two of my abilities will intermittently stop working. I cannot press the button to make them work. I cannot click on the icon on the toolbar to make them work. The two abilities are EPS transfer and Tactical Team. Moving these abilities to different locations on the hotbar has not helped either. I am not trying to activate Tactical Team when there is another Team cooldown in effect. I had the abilities mapped to ctrl-2 and ctrl-4 and then moved them to 2 and 4. No change. I do not get a little 'you cannot use this ability' beep when pressing the button or clicking on the icon. It's just totally dead. The issue tends to resolve itself after switching to a new target, but not always.
This is infuriating in PvP, as EPS is a major skill for me. I will use both these skills as an opener in an attack and not having them is like a self nerf. I wish I could give more information, but that is all I have. It is possible that the keys/abilities drop out in PvE as well, but I may not have noticed because the pace is much slower.