To reproduce the problem, hover over the last value of the series. While the Tooltip enters, it causes horizontal and vertical scroll and flickers. Then, it is positioned correctly.

The issue is better observed if you increase the transition speed of the Tooltip wrapper.

Reproduction: https://blazorrepl.telerik.com/cREDloaV42j7Z19G13.

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A possible workaround for the time being is to alter or stop the Tooltip animation with CSS. Here is a runnable sample demonstrating the approach: https://blazorrepl.telerik.com/QnEjvIOC04hXA6W709