Ember Data 0 Payload Empty Content-Type

It seems to be somewhat sporadic, and I myself have not been able to replicate the issue using similar hardware, but on Mobile Safari, I am occaisionally seeing errors in Raygun (error tracking software) similar to:

Ember Data Request GET api/v1/sales/recent returned a 0 Payload (Empty Content-Type)

Mozilla/5.0 (iPhone; CPU iPhone OS 9_3_4 like Mac OS X) AppleWebKit/601.1.46 (KHTML, like Gecko) Version/9.0 Mobile/13G35 Safari/601.1

Trouble is, investigating the logs, I see no requests to that API failing at those times, (200 or 304 statuses) so I'm wondering what could possibly be happening and whether this is an Ember Data issue or if perhaps my API is responding with something ED doesn't like.

DEBUG: -------------------------------
DEBUG: Ember      : 2.4.5
DEBUG: Ember Data : 2.4.3
DEBUG: jQuery     : 2.2.4
DEBUG: -------------------------------