Hello Armin,
We have tried to reproduce the issue you described with our latest binaries. The result was that the buttons are always displayed in small state. Also we tested the issue with older binaries(Q3 2012) and then we reproduced the issue you are describing.
As the
RadButtonGroup is designed to allow you to layout more precisely your buttons in the
RadRibbonView and specifically to
display them in small state at all times. This means that the main purpose of the
RadButtonGroup is to display all buttons it contains in a state where only a
SmallImage (by default with size of
16x16px) is displayed. That is why displaying the buttons in small state even if you set their Size property to Large in xaml is considered for correct behavior.
I hope this information helps.
Regards,
Kiril Vandov
Telerik