PVP Defense team resetting to team in #1 team slot

What you were expecting to happen, and what actually happened?
I expect my PVP Defense team to stay the way I set it, but over the last week or so, when I first log on in the morning, I notice my Defense team has been reset to reflect the team in my #1 team slot instead of the team I specifed.

What are the steps to make it happen again?
When I log on in the morning, I check my Defense team and it has been reset to the team in my #1 slot. I then set it back to my preferred PVP Defense team and check it periodically during the day to see if it stays set (and it does). The next morning, it is reset again. I thought maybe this was being caused by playing on both PC and mobile, so I have not played on mobile the last few days and am still experiencing this issue.