The ordering is due to the way objects with transparent materials are sorted. User is using them for Opaque cards, he needs to check IsOpaque on the Widget Component to fix the sorting.
If the user uses multiple 3d Widget components with in a single actor they are rendered in order of the closest widget to the screen. This can cause widgets that are behind another widget to clip into the front.
This happens in the viewport as well as in game
Head over to the existing Questions & Answers thread and let us know what's up.