If the static headers for RadGrid are enabled the scrollbar will be shown only in the area where the items are displayed. If the UseStaticHeaders property is set to false the scroll will have the same height as the RadGrid. Additional information on static headers and scrolling is available in the following article:
If you are not using static headers and I have misunderstood your scenario would you elaborate more on how is the scrollbar displayed? Please describe in greater detail what should be the expected behavior? I would appreciate it if you could provide a screenshot showing the problematic behavior.
Additionally, would you try to place only the RadGrid on the page and see if the problem would still be observed? This could help in finding what may be causing the issue.
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