Hi Oleh,

The described appearance might occur when the DropDownList/ComboBox is used inside the PanelBar content element, as there are styles applied to the PanelBar that will effect also the nested widgets. However, in such scenarios the DropDownList and ComboBox popup.appendTo option should be used:

- https://docs.telerik.com/kendo-ui/api/javascript/ui/dropdownlist/configuration/popup#popup.appendTo

- https://docs.telerik.com/kendo-ui/api/javascript/ui/combobox/configuration/popup#popupappendto

You can wrap the element from which the DropDownList/ComboBox is initialized.

<li><span id="ddl-container"><input type="text" id="ddl"/></span></li>

Then use the popup.appendto option to position the popup

 popup: {
          appendTo: $('#ddl-container')
}

You may also need to set the top and position of the animation container:

<style>
      .k-animation-container{
        top: initial !important;
        left: initial !important;
      }
 </style>

Here you will find a Dojo example where the described above is implemented and the popups are rendered on the expected places. 

I will proceed and will mark the issue as 'Declined' as the described appearance is expected in such a scenario.

In case you have additional questions or comments on the matter, please let me know.

Regards,
Neli
Progress Telerik