I get the same problem about every 3rd or 4th pull in Rahz.
I pull pair of mobs, as they get near / cast something I FD, cancel FD by walking backwards and throw another Star, FD, walk backwards, throw another star at whichever seems to be walking slower (fractionally and prob coz of angle/path).
After 3rd FD this is the one that can sometimes Cause 'FD has been toggled off'' but more importantly this causes global cooldown so the FD i was after takes 2 clicks and a cooldown i wasnt expecting.
so summary
Pull,
a. FD,
b. Walk backwards to cancel fd,
c. fire off throwing star,
d. goto a
(3rd time almost always causes Toggle off message and cooldown)
Hope this helps as the bug is quite frustrating and always leaves me roadkill

Peasant (Monk of Cairdeas)