javascript - Textarea moving up when scrolling in BootStrap -


i have problem in application have developed in bootstrap.the problem have modal body max-height setted. contains textarea,now when tap on textarea gains focus(correct till now) when scroll down text area in modal-body shown above modal-header, shows type of duplicacy of textarea. stop scrolling gone perfect again.

<div id="textpanel" class="modal fade"> <div class="modal-dialog">     <div class="modal-content"  style="padding-bottom: 5px">         <div class="modal-header">             <button type="button" class="close" data-dismiss="modal" aria-hidden="true">&times;</button>             <h4 class="modal-title">add/edit text</h4>         </div>         <div class="modal-body" style="overflow-x: auto">             <div class="row">                 <div class="col-12">                     <div id="textpreviewpanel" class="outer"                          style="height: 60px;margin-bottom: 5px;margin-top: -15px">                         <div class="inner" style="height: 100%">                             <img id="textpreview" style="height: 100%;text-align: center"/>                         </div>                     </div>                 </div>                 <div class="col-12">                     **<textarea id="addtextinput" ng-model="addedittextmodel" placeholder="enter text here"                               rows="3"                               class="form-control" style="resize: none"></textarea>**                  </div>