To reproduce:
- Add a tab to a RadRibbonForm form.
- Collapse the ribbon and press the Alt key to show the KeyTips.
- Select a tab by pressing the corresponding key.
- You will notice that the tab is not expanded.

Workaround:
void radRibbonBar1_KeyTipActivating(object sender, CancelEventArgs e)
{
    keyExpanded = true;
}

void radRibbonBar1_Click(object sender, EventArgs e)
{
    keyExpanded = false;
}

bool keyExpanded = false;

void radRibbonBar1_CommandTabSelected(object sender, Telerik.WinControls.UI.CommandTabEventArgs args)
{
    if (!radRibbonBar1.Expanded && keyExpanded)
    {
        radRibbonBar1.Expanded = true;
    }
}