GF ability Knight's Valor stops working

gimplekin

i noticed this the other day and it's happened a number of times since. the encounter ability "knight's valor" will become unusable. it sits there in the bar off cooldown, slightly highlighted. but clicking it doesn't do anything. if i die, or zone it works again, but until i do one of those two things i have to swap it out and use a different ability. i haven't been able to determine what causes the bug as its always in combat and i just happen to notice that the ability isn't functioning when i'm trying to use it. i'm level 60, and this is in group instances as i don't use the ability while solo, heroics, normals, skirmishes.