DataFlow Gen 2 Error:Fast copy user error

Totally understand that there were no settings at the query level, but would you mind checking if the Fast Copy setting at the Dataflow level was enabled? 

You can see this inside the Options > Dataflow > Scale tab

You can turn this setting off and your Dataflow will not try to use Fast Copy unless you explicitly use the setting at the query level.

Complex values like [Table] values can create some situations that would prevent Fast Copy to behave the way its intended. It also happens with how Staging that table would yield the same column but with null values as you cannot store "Table" (complex values) into a staging table.