We found extra characters at the end of JSON input

Hi hmeltonPSL 

Since "The URL works fine on its own and get JSON back", you can try using Web connector in Power Query Editor to connect to this URL and test whether it can get the result back. You will need to enter credentials before connecting successfully. Power Query will detect the format of the data it gets and convert it to JSON format automatically. 

If you can get correct result from the URL through Web connector, then you can use a query paramter to replace the projectid part in the URL. At last, in Queries pane, right click on the query and select option Create Function. This method is to use UI to create a function. You can compare its M codes and your codes to see which the difference is that may cause the error.

Regards,
Community Support Team _ Jing
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