We've experienced this for many years running NAV2013 via RemoteApp on a Win2012R2 host, and after rolling out NAV2018 via RemoteApp on a Win2016 host the problem has continued.
Intermittently users will run the RemoteApp shortcut on their workstation and the blue NAV splash screen will show.
This will then disappear as normal but instead of displaying the entire dashboard they are left with just an empty white NAV window.
To correct this an admin must RDP into the server, end-task the NAV RTC client for that user and logoff that users session and ask them to try again.
This bug is somewhat identical to one I found during many google searches that occured with NAV2013 and Citrix environments.
Any suggestions on a cause/resolution?