Event ID 103 — The disconnect reason is ReasonCode.

{
  "system": {
    "provider": "Microsoft-Windows-RemoteDesktopServices-RdpCoreTS",
    "guid": "1139C61B-B549-4251-8ED3-27250A1EDEC8",
    "event_source_name": "",
    "event_id": 103,
    "version": 0,
    "level": 4,
    "task": 4,
    "opcode": 17,
    "keywords": 4611686018427387904,
    "time_created": "2019-08-27T17:16:34.852505Z",
    "event_record_id": 857,
    "correlation": {
      "#attributes": {
        "ActivityID": "F420DD64-C87E-4E2D-A02E-7D0935770000"
      }
    },
    "execution": {
      "process_id": 636,
      "thread_id": 6492
    },
    "channel": "Microsoft-Windows-RemoteDesktopServices-RdpCoreTS/Operational",
    "computer": "MSEDGEWIN10",
    "security": {
      "user_id": "S-1-5-20"
    }
  },
  "event_data": {
    "ReasonCode": 14
  }
}