I was getting the same error in PPT 2016 over and over again out of nowhere after many successful attempts at video creation. I am using inserted audio that starts at the beginning with recorded slide times. I noticed that I had the little speaker icon on every single slide and it was checked to play across slides that wasn't there before. I deleted every speaker icon on each slide except the first one, made sure the sound was still sert to start in the Animation Pane, and unchecked "Play across slides" (although it still played correctly across each slide). After that, the video finished without an error and the checkmark reappeared by "Play across slides" (although the speaker icon is gone after the first slide). Maybe this will work for someone else. :-)