Error in creating Observation

[kuldeep singh]

Hi, I am getting "Internal service error from resource store" while creating Observation
with
X-Request-Id :--- 96be9535-2113-4ef4-a413-0b36f4dd02bc+2673

body
{
  "resourceType": "Observation",
  "status": "final",
  "category": [
    {
      "coding": [
        {
          "system": "http://terminology.hl7.org/CodeSystem/observation-category",
          "code": "vital-signs",
          "display": "Vital Signs"
        }
      ],
      "text": "Vital Signs"
    }
  ],
  "code": {
    "coding": [
      {
        "system": "http://loinc.org",
        "code": "8331-1"
      }
    ],
    "text": "Temperature Oral"
  },
  "subject": {
    "reference": "Patient/12798429"
  },
  "encounter": {
    "reference": "Encounter/97845408"
  },
  "effectiveDateTime": "2020-04-03T19:21:00.000Z",
  "issued": "2020-04-03T19:21:40.000Z",
  "performer": [
    {
      "extension": [
        {
          "valueCodeableConcept": {
            "coding": [
              {
                "system": "http://terminology.hl7.org/CodeSystem/v3-ParticipationType",
                "code": "LA",
                "display": "legal authenticator"
              }
            ],
            "text": "legal authenticator"
          },
          "url": "http://hl7.org/fhir/StructureDefinition/event-performerFunction"
        }
      ],
      "reference": "Practitioner/12799006"
    }
  ],
  "valueQuantity": {
    "value": 37.2,
    "unit": "degC",
    "system": "http://unitsofmeasure.org",
    "code": "Cel"
  },
  "interpretation": [
    {
      "coding": [
        {
          "system": "http://terminology.hl7.org/CodeSystem/v3-ObservationInterpretation",
          "code": "N",
          "display": "Normal"
        }
      ]
    }
  ],
  "note": [
    {
      "authorReference": {
        "reference": "Practitioner/12799006"
      },
      "time": "2020-09-03T15:03:10.000Z",
      "text": "No additional test require"
    }
  ],
  "referenceRange": [
    {
      "low": {
        "value": 35.8,
        "unit": "degC",
        "system": "http://unitsofmeasure.org",
        "code": "Cel"
      },
      "high": {
        "value": 37.4,
        "unit": "degC",
        "system": "http://unitsofmeasure.org",
        "code": "Cel"
      },
      "type": {
        "coding": [
          {
            "system": "http://terminology.hl7.org/CodeSystem/referencerange-meaning",
            "code": "normal",
            "display": "Normal Range"
          }
        ],
        "text": "Normal Range"
      }
    }
  ]
}

Other doubts:-
1)If I am using Patient Id 12457981 than I am able to create observation why?
2) If some fields are missing in my patient id 12798429 , can u provide the template for creating patient that can be use in Observation creation