From watching the replays, the time situation is a non issue, it was done to the letter of the law. As per TV time: 78:30 try scored, 78:33 try awarded and clock stopped. Clock resumed once try was confirmed, 80 seconds (actually 82 seconds) later clock stopped as per rules for conversions (79:55 on TV, but 6 seconds on the official clock from looking at the scoreboard). Ball hits the upright at 79:56 (so with 5 seconds left on official clock), and the ground at 79:57 (so 4 seconds left). Clock stopped at 80:00 on the TV clock (but 1 second left on the official clock as shown with TV clock being 1 second ahead). Clock updated on TV to reflect correct time. Therefore clock was accurate.
The rules breaches were in the accepting of the challenge when there was no stoppage of play, and the incorrect ruling of obstruction.