dawdle draught sometimes still fails ...
on two separate occasions this week during LOH Potions Classroom event ( and i witnessed the second time, after she had complained to me about the first time a day earlier), she popped both a dawdle draught AND a strong exstimulo potion when a Harry Potter trace spawned. yes, i saw her engage each potion with the potion animation confirming its use. each time, on the very first spell that she cast, the Harry Potter foundable disintegrated/whisked-away and the engaged dawdle draught did not kick in to prevent it - no departure denied.
when she opened up the next trace encountered, she sees (and i witnessed on second time) that her dawdle draught counter is at 2/3 and her strong exstimulo potion counter is at 3/4. potion carryover now wasted on lesser traces that follow, with no realistic ability to save for plumed traces that could use the boost.
so, two dawdle draughts and two strong exstimulo potions, and brew times, wasted.