The glitch on the screenshot indicates that there are CSS styling issues. Try removing all the CSS styles and stylesheet references from the page then test the application again. If the built-in styles are broken, please share the Grid configuration you are using (markup and server-side code) so we can replicate the issue and we will tell you how to fix it.
A Common issue is if using Virtualization and setting the Rows height to percentage value via CSS. This is known to break the application appearance and it is not recommended. See the Virtualization Limitations section.
Eventually, I will need to see the Markup and server-side code of the Grid you are using and will be able to tell you more.
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