What you were expecting to happen, and what actually happened?
What are the steps to make it happen again?
Do you have any screenshots or video you want to share with us so we can see the problem? Attach them to your post!
When I cast Mercy AFTER casting Dawnbringer it removes barrier from all my troops. It has never done this before. I have been using these two troops in my pvp attack team for a very long time.