SearchBirdseyePositions offset requests return 'no results'

I am having trouble with getting the SearchBirdseyePositions to reliably return results. Based on this other post (Assistance with SearchBirdseyePositions) I am curious if the request is timing out on the backend.

Here is the request I am sending, with an offset of 0 it succeed about 50% of the time and the subsequent requests usually return 200, but with an “error: no results” payload.

http://flightxml.flightaware.com/json/FlightXML2/SearchBirdseyePositions?query={range+lat+29+30}+{range+lon+-82+-81}&uniqueFlights=True&howMany=15&offset=30

bump

Still not sure how best to scope this query to get reliable results