Sometimes cards stall out once they fill their cooldown bar? Seems like either cooldown buffs or cooldown advancements aren't being registered by the game? I had the acquire medium -> reduce cooldown effect applied multiple times to the scaling Nar gatherer. It seemed that he waited for his original cooldown rather than his upgraded one, just waiting once his progress bar filled. I had a duplicate of him in my board at one point and thought maybe that was causing it but it still happened after selling the duplicate.