Crashing on loading ACT2 Cruel - Dreadnaught Vanguard Boss checkpoint

I was playing right after the patch, got to clear the last map of act 2 cruel, died on the boss after phase 2, got booted to character selection screen.
Now when I try to log back in I get "Unexpected error" and I get taken back to the character selection.

Issue seems to have been solved "on his own"