If the height of RadComboBox is set to a value smaller than 26px (in Office2013) then the content of the RadToggleButton presenting the selected content is clipped.
This was reproduced with the Office2013 theme.
To work this around set the MinHeight of the child RadToggleButton to the same MinHeight as RadComboBox.
When you start navigating through the ribbon via the keytips or the arrow keys, and you get to a RadRibbonComboBox, this opens its drop down which contains RadRibbonComboBoxItems.
In this case the keyboard navigation (using the arrows) of the RadRibbonComboBox doesn't work. This happens because the ribbon navigation implementation interfere with the combobox navigation.
Available in the R1 2017 SP1 Release.
Available in LIB version 2016.3.1017, it will be also available in the 2016 R3 SP1 release.
When the ComboBox is non editable.
When IsEditable is set to true the SelectedItem is not updated if you delete the SelectedItem's text to match another existing item.
When the CheckBox is focused the issue is appearing. Available in LIB version 2016.2.905, it will be also available in the 2016 R3 Release.
The same issue can be observe when placing the control inside ToolBar.
When you click on the TextBox of an editable RadComboBox all the text should be selected, but it is not, even when SelectAllTextEvent="All" is set. The text is blinking as selected for half a second and then deselects.