Circle Form Fail under Marsmallow!

Hallo @Terry , We tried to make a circle form in an app the we created under Marsmallow and the result is always oval form (the horizontal is wider than the vertical once). We tried to change with the Nougat and it works. The problem, we already finished the app base on Marsmallow and it will be so much work to replace the OS to Nougat. Any solution?