Guild Wars 2

During several missions, “Eye of the Sun” and the “Victory or Death” story of the “Arah” dungeon, to name a few, there is a requirement to man a turret.

If you get hit by an enemy or an AOE attack, your skills return to those assigned to the weapons you have equiped, but you are still “at” the controls of the turret.

The green “Leave” marker is still onscreen, but pressing “F” or clicking on it with the mouse does nothing, you’re stuck at the turret.

During “Arah” my character couldn’t use any skills at all, and ended up dying, after several attempts at using the turrets during the various battles.

During “Eye of the Sun” another character was able to use her weapon skills to fight off her attackers. (The accompaning NPC’s simply stood there the whole time.)
After surviving the onslaught, I still couldn’t leave the turret. I tried every skill, swapped weapons, and as I was a Thief, when I used my Dagger skill, “Heartseeker,” I jump toward the boss, reconnected with turret and finished the quest.

It’s happened in other quests too, I simply can’t recall which ones.
It always occurs after taking damage. (Never noticed how much damage as I was concentrating on targeting the turret.)