I was playing a DMU Traditional Draft and my opponent blocked with a Tattered Apparition and activated it more time than the untapped lands the client displayed should have allowed them to. This happened two times with Tattered Apparition, and they also appeared to activate Tidepool Turtle with only two mana. I can only assume the client was not correctly displaying the state of their lands and they were seeing something different than I was. This caused them to gain an advantage and win the match as my plays in these cases assumed what I was seeing was correct and were only sound if that were the case. I additionally experienced issues with the client taking a long time to acknowledge certain changes in game state such as starting turns, but not others. I don't know if that is related, but it seems like it might be.