Do you use custom map markers in your app? If you do set ShowUsers from properties strange things happen when you set the ShowUser icon using Map Properties with some Blocks.
see
Custom Map User Icon - #7 by SteveJG for another example. Evidently using ShowUser creates issues depending on what Blocks are used in the app. I don't know whether this is an MIT feature or intentional.
The ShowUser definitely is not wired correctly and buggy in certain circumstances. 