Please try installing the latest update for your Surface Duo that was released on May 27th:
- On your Home screen, tap Settings.
- In Settings, tap System > System update > Check for update.
- After the update is downloaded and installed, tap Restart now.
More information about update can be found here:
Surface Duo update history (microsoft.com)
Please respond back if you installed that May 27th update and you are still seeing one of the screens on Surface Duo go black periodically.