Thank you so much for finding this endpoint Bruno I was having the exact same issue, not sure why this kind of stuff is hidden from us.
One important thing to note is that in my experience even when the single account aggregation fails, the “status” field still shows SUCCESS. The “resultJson” field, though, contains a sub-field called “accountErrors” that shows a 1 if the single account aggregation had an error and a 0 otherwise. I’m actually unsure why the resultJson in your example seems to be null.