Bug-Perma silence from gray debuff crystals.
This was encountered on PC. While playing online with friends as Wulfgar I got perma-silenced by the gray crystals in Goffin's Door. Even after we destroyed the first batch I was stuck with the debuff until we found another patch of gray crystals way further in the level. These new crystals refreshed the silence debuff and after we blew them up it finally disappeared. THIS WAS NOT A GRAPHICAL BUG! It legitamely prevented me from using all abilities except my ultimate. Sorry I didn't screenshot it, i will if it happens again.
I would like to add to this, I encountered the perma-silence as well, and it followed me back to base camp! I have attached an image!
Have had the same thing happen on multiple occasions and to all members of the party at different times. Shatter the grey crystals and silence debuff is permanently on blocking all abilities. Have had to go through entire levels not being able to use abilities.