I have noticed a strange display issue with Horizontal Scroll bars when resizing a RadDocumentPane that contains a RadGridView control.
When a GridViewColumn is set to star width sizing, and the width of the RadDocumentPane is reduced by dragging the splitter across, a Horizontal Scrollbar appears temporarily as the splitter handle is released by the mouse, then disappears again, even though there is plenty of horizontal space and no need for it to show.
If the width is set to Auto then the problem goes away.
Here's the xaml (nothing fancy in CS so don't bother posting):
Are you able to replicate this?