Do not force or assume transformations when Power Query gets data.

I have used Power Query as part of Power BI and Dynamics 365 Customer Insights. In both cases when Power Query is used to connect to data in Dynamics 365 (Dataverse) Power Query converts all GUIDS to uppercase.

Dynamics 365 stores GUIDS in lowercase. When Power Query forces this transformation, it breaks the relationship between the system of record (Dynamics 365) and the Power BI report or the Customer Insights environment. In order to restore the relationship the user has to manually add a lowercase transformation.

This seems like a bug in Power Query. If this is an intended feature, we should at the very least, be able to turn it on or off.