Turkish characters saved to database in incorrect format when using Angular textarea control

Question

I noticed that Turkish characters get saved differently, based on the specific HTML element control being used (correctly for textarea, incorrectly for input).

I am using the following characters for my test: ÖŞĞÜİÇ öşğüıç

Below is my HTML for the input and textarea controls (nothing fancy):

<div class="col-md-12">
    <div class="row defMarginBottom">
        <div class="col-md-6">
            <label>Mesaj Konusu</label>
            <input type="text" class="form-control" placeholder="Konu"
                   ng-model="titleText" />
        </div>
    </div>
    <div class="row defMarginBottom">
        <div class="col-md-3">
            <label>İnternet Adresi Konusu</label>
            <input type="text" class="form-control"
                   placeholder="İnternet Adresi Konusu"
                   ng-model="additionalDataSubject" />
        </div>
        <div class="col-md-3 defMarginLeft1_3">
            <label>İnternet Adresi Linki</label>
            <input type="text" class="form-control"
                   placeholder="İnternet Adresi Linki"
                   ng-model="additionalDataLink" />
        </div>
    </div>
    <div class="row defMarginBottom">
        <div class="col-md-6">
            <label>Mesaj</label>
            <textarea class="form-control defHeight"
                      placeholder="Mesaj" ng-model="message">
            </textarea>
        </div>
    </div>
    <div class="row">
        <input style="margin-left:1.5%;" type="button"
               class="btn btn-success" value="Kaydet ve Gönder"
               ng-click="saveAndSend()" />
    </div>

</div>

Following is the Angular Controller code where the ng-models are defined:

var jsonObj = {
    "Subject": $scope.additionalDataSubject,
    "Link": $scope.additionalDataLink
};

var obj = {
    "ActivityTypeIds": activityTypeIdList,
    "SalesPersonID": $scope.salesPersonId,
    "SalesPersons": $scope.spIdList,
    "CustomerCategories": categoryIdList,
    "customerName": $scope.customerName,
    "StartDate": $scope.startDate,
    "EndDate": $scope.endDate,
    "TitleText": $scope.titleText,
    "Message": $scope.message,
    "AdditionalData": JSON.stringify(jsonObj)
};

When I enter the test strings, only those for the textarea controls get saved properly to the database.

Those for input controls are saved incorrectly as: ÖŞĞÜİÇ öşğüıç

Note: I recently added the following new directive to my Angular app as a protection agaist XSS attacks, and was suspicious of it as causing the problem, but since the entries for textarea are saved correctly, I'm not sure if it is related.

.directive('input',['$sanitize', function ($sanitize) {
    return {
        restrict: 'E',
        require: '?ngModel',
        link: function (scope, element, attrs, ngModel) {
            if (ngModel !== undefined && ngModel != null) {
                ngModel.$parsers.push(function (value) {
                    return $sanitize(value);
                });
            }
        }
    };
}]);

How can I overcome this problem? Most of the questions here on SO are about rendering of Turkish characters, not about saving them.