Bug: findMeetingTimes thows "OrganizerUnavailable" on 15 minute start times

When using the Graph API findMeetingTimes method on 15 minute start times (for example 3:15, or 3:45), the method will incorrectly throw a "emptySuggestionsReason = OrganizerUnavailable" error (and no rooms returned), whether rooms are available for that time, or not.

For example, this will error:

{
"timeConstraint": {
"timeslots": [
  {
    "start": {
      "dateTime": "2018-01-11T10:15:00",
      "timeZone": "Pacific Standard Time"
    },
    "end": {
      "dateTime": "2018-01-11T11:00:00",
      "timeZone": "Pacific Standard Time"
    }
  }
]...}

Whereas, this will not:

{
"timeConstraint": {
"timeslots": [
  {
    "start": {
      "dateTime": "2018-01-11T10:00:00",
      "timeZone": "Pacific Standard Time"
    },
    "end": {
      "dateTime": "2018-01-11T11:00:00",
      "timeZone": "Pacific Standard Time"
    }
  }
]...}

Note the "2018-01-11T10:15:00" start time.