Power Query and PowerBI currently don’t have the same definition of duplicates.
For Power Query “A” and “a” are not the same thing, for powerBI they are
For Power Query “A” and “A ” are not the same thing, for powerBI they are
So when you create relationships in PowerBI , if you get an error about records not being unique, check if those cases might apply and look into putting things in all upper or lower case or trimming strings.
Hope this helps (and hope even more this get fixed soon...)