Dataflow stop refreshing : "Expression.Error: The field 'X' already exists in the record"

I did it for the fourth table and refresh it one by one, all the table are loaded without error, I had the step with the append query has new table and it is there that I have the issue,

I am do not understand what is happening as the four source table for the append query has a unique column name but when it append the data, I have the error