When the Add Data Widget is restricted to only permit layers from AGOL, the page scroll buttons jump to the top of the widget and page numbers disappear. But if the the URL or File option is enabled, the page scroll buttons accurately appear at the bottom of the widget.
(See images attached)
Please how can this be rectified?
I just tested your workflow with Web AppBuilder for ArcGIS Developer Edition v2.4 and was unable to reproduce your issue. Suggest you upgrade to the 2.4 release.
Hope this helps,