Expected behavior When modal opens up and a user types a value in the input field, a JS function is called

Actual behavior As soon as the modal opens up the following errors appear:

Code of modal:

    <div class="modal fade" 
     id="DuplicateAction" 
     tabindex="-1" 
     aria-labelledby="myModalLabel" 
     aria-hidden="true"  
     data-mdb-backdrop="static"
     data-mdb-keyboard="false">
    <div class="modal-dialog">
        <!--Content-->
        <div class="modal-content">
            <!--Header-->
            <div class="modal-header bg-info white-text">
                <h4 class="title">Duplicate Classification</h4>
                <button type="button" class="btn-close" data-mdb-dismiss="modal" aria-label="Close"></button>
            </div>
            <!--Body-->
            <div class="modal-body">
                <form>
                    <div class="form-group">
                        <div>
                            <div id="Location-source" class="form-outline">
                                <input type="text" id="form6" class="form-control" required autocomplete="off" onchange="OnLocationChange(this)"/>
                                <label class="form-label" for="form6">Enter KKS...</label>
                            </div>
                            <div class="row">
                                <div id="locations-holder"></div>
                            </div>
                        </div>
                        <div class="form-check">
                            <div class="DuplicateCheckBox">
                                <input class="form-check-input" type="checkbox" id="DuplicateApproaches">
                                <label class="form-check-label" for="DuplicateApproaches">
                                    Duplicate Approaches
                                </label>
                            </div>
                        </div>
                        <div class="form-check">
                            <div class="DuplicateCheckBox">
                                <input class="form-check-input" type="checkbox" id="DuplicateActions">
                                <label class="form-check-label" for="DuplicateActions">
                                    Duplicate Actions
                                </label>
                            </div>
                        </div>
                    </div>
                    <input id="CreatedDate" type="hidden" class="form-control" value="@DateTime.Now.ToString("yyyy-MM-ddThh:mm:ss")">
                    <input id="CreatedBy" type="hidden" class="form-control" value="@_session.GetString("displayName")">
                    <div class="text-center mt-1-half">
                        <button class="btn btn-outline-info mb-2" data-mdb-dismiss="modal">Close<i class="fas fa-send ml-1"></i></button>
                        <button class="btn btn-info mb-2" onclick="OnDuplicateButtonClick(this)" action="#">Duplicate<i class="fas fa-send ml-1"></i></button>
                    </div>
                </form>
            </div>
        </div>
        <!--/.Content-->
    </div>
</div>

Resources (screenshots, code snippets etc.)