Execution erorr: Invalid opcode on estimateGas | Possible unhandled promise rejection

Question

pragma solidity ^0.5.0;

I get invalid opcode error when trying to estimate gas needed for my transaction from react-native using the following line of code:

const gasAmount = await contract.methods
      .Track(RecordOwner, account, meidcalRecordHash)
      .estimateGas({from: account});

After some searching, I found this answer, which states that invalid opcode can be the result of either one of the following runtime operations:

(1)assert of an expression which evaluates to false

(2)array[i] where i >= array.length

However, I do not see any of these two possible runtime operation in my solidity "Track" function

   function Track(
        address _patientID,
        address _doctorID,
        string memory _recordHash
    ) public {
        

        // Get the record hash index
        uint256 i;
        uint256 recordHashIndex;
        string[] memory patient_recordHashes = getPatientRecordHashes(
            _patientID
        );

        for (i = 0; i < patient_recordHashes.length; i++) {
            // CHANGED count to patient_recordHashes.length
            string memory patient_recordHash = patient_recordHashes[i];
          
            if (
                keccak256(abi.encodePacked(patient_recordHash)) ==
                keccak256(abi.encodePacked(_recordHash))
            ) {
                recordHashIndex = i;
            }
        }

        // Get the doctor address index
        uint256 doctorIndex;
        address[] memory patient_listOfDoctors = getPatientRecordListOfDoctors(
            _patientID,
            recordHashIndex
        );
        for (i = 0; i < patient_listOfDoctors.length; i++) {
            if (patient_listOfDoctors[i] == _doctorID) {
                doctorIndex = i;
            }
        }
      

        // Set the bool value corresponding to the "recordHashIndex" & "doctorIndex" to true
        IsRecordSeen[_patientID][recordHashIndex][doctorIndex] = true;

        // Destroy/remove the medical record from the dcotor view screen
        delete patientToDoctorRecordNames[_patientID][_doctorID][recordHashIndex];
        delete patientToDoctorRecordHashes[_patientID][_doctorID][recordHashIndex];
        delete patientToDoctorEncKeyHashes[_patientID][_doctorID][recordHashIndex];
    } // end of the Track function



//Some of the function used inside the Track function:

// Get all the record hashes of a patient
    function getPatientRecordHashes(address _patientID)
        public
        view
        userExists(_patientID)
        returns (string[] memory)
    {
        return patientRecordHashes[_patientID];
    }

  // Get the list of doctors with access to a specific medical record of a patient
    function getPatientRecordListOfDoctors(address _patientID, uint256 index)
        public
        view
        userExists(_patientID)
        returns (address[] memory)
    {
        return patientRecordListOfDoctors[_patientID][index];
    }

Is there something wrong inside the Track function that cause invalid opcode ? Any hint would be highly appreciated

Update1: I have just tested the "Track" function on remix. It is working fine. Also, the estimate gas sometimes works, but not all the time. any hint on why this is happening, please?

const gasAmount = await contract.methods
      .Track(RecordOwner, account, meidcalRecordHash)
      .estimateGas({from: account});

some data structures used :

mapping(address => mapping(address => string[]))
    public patientToDoctorRecordHashes;

mapping(address => mapping(uint256 => address[]))
    public patientRecordListOfDoctors;

mapping(address => string[]) public patientRecordHashes;







mapping(address => mapping(uint256 => bool[])) public IsRecordSeen;

Update2: Please note there is also an "Add" function that is usually called before the "Track" function. This "Add" function has multiple "push" operations inside. some of these push operations are:

    patientRecordHashes[_patientID].push(_recordHash);
    doctorListOfPatients[doctorAddress].push(_patientID);
     patientToDoctorRecordHashes[_patientID][doctorAddress].push( _recordHash);
    IsRecordSeen[_patientID][count].push(false);