opponent never finished move and then....

I was playing a Mega Venusaur deck against a Mega Charizard deck. I had 2 prize cards left, he had 1 prize card left. I had my Meganium in active, he got a rare candy and went to evolve his charmander into dark charizard ex. He stopped at the energy collection because apparently he didn't have enough to add so he could kill Meganium and take the win. His charizard sat in the air not attaching energy for the entire 13 minutes left of his timer. It never "timed out without moving. Then it sat there at 0 minutes left. I had to close the window by turning it off directly from the logo on the task bar. What causes that kind of bugginess? And can it be fixed? Thank you.