On Build 1903 Preview, when connected to a Server 2012 R2 system, navigating to the Files extension generates the following error:
Notification details Error Failed to load This PC. Error: RemoteException: The term 'try' is not recognized as the name of a cmdlet, function, script file, or operable program. Check the spelling of the name, or if a path was included, verify that the path is correct and try again.
From this point, the circles spin and never load the files tree. This issue does NOT occur when connected to Server 2016 servers.