it happen very often when you have many buffs up that turbohud ist drawing the icons (above your skillbar) on the wrong position and covering other icons.
this bug is very old. i did not report it yet. and other players in my party confirmed aswell.
it seems like the buffs given by other players are not drawn anyone more (like ignore pain or mantra buffs).
the result is that "ui_default_buffs" is covering important buffs like "ignore pain" with other icons.