Hey @peter,
We took a look and were able to identify an issue with the API and the time_start parameter. We are incorrectly handing a start time of 3:36 AM UTC and starting to pull observations at 3:45 AM UTC. You can test by setting time_start to 4/18/18 3:30 AM UTC and you will see that you will correctly get observations back starting at 3:30 AM UTC.
https://swd.weatherflow.com/swd/rest/observations/device/1110?api_key=20c70eae-e62f-4d3b-b3a4-8586e90f3ac8&time_start=1524022200&time_end=1524033360
We’ve added this bug to our list and it will be fixed in a future API update. Thanks for letting us know!