Won't flatten array of strings

[Douglas de Oliveira Mendes]

https://www.csvjson.com/json2csv/d3542c542a13f3546a5b58318f6cc2f3

It's a valid JSON but won't convert when the checkbox "Flatten" is checked. Instead, the following error is presented:

Item in array is not an object: "A"

[Haydn Morris]

I'm also running into this - did you manage to find a workaround?