Non-native dialogs have wrong size on Windows Phone 8.1/10

Non-native dialogs (such as dialogs based on AbstractDialog) have randomly wrong size on Windows Phone 8.1/10. Sometimes they are bigger than the screen dimension, sometimes they are tiny and are showing only a "some" pixel small rectangle on the top left.

Steps to reproduce (attachment):

• Click on timer button to continously open and close a sample dialog. Usually the problem is visibile immediately.
• If the problem does not show up then completely kill the app (press-and-hold back key) and start again.
• The problem shows up more often in release mode.