I am getting below error while performing step 2 "Upgrade New Version" in nav 2013 R2. i have probablly checked all possible actions to perform, sync-navtenant is done successfully and no compilation issue in object. one thing to notice here is, i have around 400 companies in database and database size is 30 gb. yes it took long time(12 hours) in Sync-NAVTenant but there was no error. 

i tried all possible reasons described in this link https://cloudblogs.microsoft.com/dynamics365/no-audience/2014/03/27/the-new-table-synchronization-paradigm-in-microsoft-dynamics-nav-2013-r2/?source=nav

The following SQL error was unexpected.
The nvarchar data type cannot be selected as DISTINCT because it is not comparable.
Statement(s) could not be prepared.