Hello Guillaume Crétot Richert,
Thank you for contacting us back.
I see, the reason for that is that autosize uses the size of the inner controls which in the case of RadButton is set to 0. The workaround is to set the row to absolute and use for the size of the row the height of the button. Sorry for the introduced inconvenience.
Do not hesitate to write me back if you have further questions.
the Telerik team
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