I am currently experienced issue with Power BI Desktop Loading data from Dataflow.
The column h_WC-combine is created in Dataflow online which is the concatenation of two other columns. When loading data to the Power BI Desktop, some (not all) data of this column returned blank, despite the fact that both source columns has data or non-null.
I went back to Dataflow and check, the exact record on Dataflow showing value, but Power BI Desktop did not.
Then I created a new custom column concatenate the same 2 source columns in the Transform - Power Query Editor, result return correct, which confused me even more of why data was load from the Dataflow was process differently?