According to the provided sample code and the image demonstrating the problem it seems that the splitter has incorrectly calculated its size. This behavior might occur in case the splitter's wrapper (<div class="context" >) is also incorrectly sized.
Could you try to set height smaller to the space between header and footer (for example 300px) 'context' div and see if the splitter will be sized correctly?
All the best,
the Telerik team
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