the bug is long standing and basically happens when a character is out of combat [because invis or too far away, hiding etc] when the cut sence starts... at the end of that combat this character is left in limbo land unable to react to the rest of the world and the only fix is to load another save and start again
as of this patch 9 Larian changed most vid cut sences to auto select the main character in a bid to fix this bug... it didn't work of course but i see their logic
