To reproduce: please refer to the attached sample project and gif file. Workaround: use screentips: https://docs.telerik.com/devtools/winforms/telerik-presentation-framework/tooltips-and-screentips/screen-tips
Currently, RadTooltip takes the focus because its owner is another control. When the tooltip is shown its take the focus from the control and control hide the tooltip, and after that, the control received focus and show tooltip again.