The AsyncPostFromString function's events will only return the Response body if the HTTP Status Code = 200.
While this probably covers most scenarios, it *should* also return the response body for HTTP Status Code = 201 ("Created"). Currently, it does not. This is actually a pretty big omission since a 201 is a "more correct" response code for certain scenarios.
This one cost me a couple of hours so hopefully it helps someone (and hopefully we can get 201's added for future releases). 😉