Guild Wars 2

Liking the gauntlet appart for some details so far, but i got a question.

The tremor gambit, as far as i have seen, knocks u and the boss both arround in an interval.

Now i noticed it happen a few times that even if i dont take that gambit, sometimes ill still have the effects of tremor, but just on me, the boss stays untouched.

The question is does any of the bosses have that mechanic or is this some kind of known bug?

happened to me 3 times today.