The provided information is not enough to determine the exact cause of the problem. According to the screenshots, I believe you are using custom skin for RadSplitter. If this is the case, could you please try to use one of the built-in skins and see if the problem still exists?
Also, from the screenshots it not possible to determine if the displayed scrollbar is the browser's scrollbar or a scrollbar of the pane. Could you please provide sample page and / or a live URL reproducing the problem so we can examine it further?
All the best,
the Telerik team
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