To reproduce:
- add RadRibbonbar with two groups;
- add several RadButtonsElements in each group;
- subscribe for the ToolTipTextNeeded event:

private void radRibbonBar1_ToolTipTextNeeded(object sender, ToolTipTextNeededEventArgs e)
{
    e.ToolTipText = sender.ToString();
}

If you hover a certain button, the tool tip for button element appears, which is correct. If you hover precisely the ribbon bar group, the correct tool tip also appears. But after that each element hovering, displays the wrong tool tip.