I’ve had this twice today, unsure how to recreate specifically as it was in a bit of chaos when it began.
Using a whirlwind barbarian with whirlwind and lunging strike and all 4 shouts. At some point, my lunging strikes become super slow motion and I cannot use whirlwind even with full fury. Shouts and potions are working fine.
Seems to only be resolved when leaving the dungeon.
I have a video if helpful.