Some static UI is causing constant layout updates and severe reduced FPS on UI that does not have any visible changes to it. These layout updates continue even if the UI is hidden (Visible = false or Enabled = false).
Here’s a screenshot of the microprofiler showing the long layout updates:
This issue goes away if AutomaticSize is turned off for all items. Still, the UI should not be updating its layout when nothing about it or the screen is changing.