FIX: Shared user can only be changed by himself/herself
When trying to edit a user you get the error message: "Shared user can only be changed by himself/herself"
You are trying to edit a user which is shared between multiple applications. And the user has _EditUser privileges in more than one application.
Most likely you have created an overview application, and when copying the vehicle/user to the overview application you have not changed its Role from _Administrator to _Unit.
The other main cause is that you have added the _EditUser privilege to the _Unit Role in the overview application.
Make sure that your shared users does not have _EditUser privilege in the overview application. Only have _DeviceLogin active for the _Unit Role, and only make shared users/vehicles member of the _Unit Role in the overview application.
There is a useful feature in SiteAdmin to login "impersonated". In the application list in SiteAdmin click on the icon left to the name of the application, then select the username to login as. In this way you can verify that a user gets the proper experience when logged in.
How to move users between applications, and how to add users to multiple applications
A very useful feature is to right click on a user/vehicle in the vehicle list and select "Overview". In the Window that opens you can see which exact Roles and Privileges this user has in the application.