Trials of Chaos...Bugged negative?

Doing a lvl 79 Inscribed Ultimatum, and chose the "Unstoppable monsters" negative, which is never a problem with my speedy Gemling.
But now I move at half speed instead. Can't say for sure if monsters are affected or not as it never hinders me in any way, usually.
Tooltip says "Monsters cannot be Slowed or Stunned", but nothing has ever applied to MY movement speed before.

Without anything different happening, apart from my getting more negatives as the rooms went on in the trial, i got my normal movement speed back... Very odd. :O
When this hindrance occurred, i always had movement speed -1.1%, no afflictions showed at all. It just came and went for a few rooms without anything explaining it. :O

Doing a second run, chose the same negative affect "Unstoppable Monsters", no hindrance in movement this time. So i was not able to replicate the unwarranted effect.