I've got a suitelet that returns a JSON string to a client script via a client initiated

<http://https.post|https.post>

. The client script and suitelet seem to be working correctly except that the response is empty. The suitelet completes running without errors and logs the response data just fine, but it never gets to the client. The client script meanwhile fails the promise and in the

.catch()

gets only an empty error. How would you troubleshoot this?