DataFormat.Error: We found extra characters at the end of JSON input.

Hi all, 
I had the same issue but I was making the called with the function and from a different query. The issue is to parse the call  before it gets the JSON, The other way is to have the JSON open as text and parse it using a technique mention in a post from ExcelGuru: https://www.excelguru.ca/blog/2015/11/19/keep-only-numbers-in-power-query/ 

They remove nothing but numbers I change to nothing but Special characters, you can add more if you want to here is my code for the list that you load before doing any changes. 

CharsToRemove = List.Transform({33..45,47}, each Character.FromNumber(_))

Then, you can add a custom column: 

"Column name"
Text.Remove([Call elementclean],CharsToRemove)

This case not sure if it works from Azure SQL like this but you should try it in SQL. 

Hope this help someone. 

Best,
J