Strange error with calculation

Hi,

I have a problem with Power Query, I absolutely don't understand:

We get data from SAP which we store in a folder by month - below you see the import text for the single files - only query name and filename changed, the query was done once and then duplicated.

Then they were  appended by year and finally the 3 years were appended - in the totals queries there is only the one line of code you can see below, I only shortened the months statement a bit in the middle. 

My problem: in Power BI we realized that the numbers for November, 2021 were duplicated - just for November, 2021!

I had all queries' rows  counted, the numbers were perfect for all month and for all single-year queries, in the query Totals 2020 - 2022 the miscalculation all of a sudden appears. There I have double the amount of rows for November, 2021, and the entire query statement is shown above. I can't understand that logic! I finally solved the issue by removing duplicates from the entire table, but I would consider that only as a workaround.