Ribbon menu button disable enable.

Hi
I made a exampel file of the ribbon
There is one thing i don't understand.
I can enable one control with the following code
When i trye the same code like for enable for disable it not working

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The only thing i found until now is disable all controls

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How to disable one crontrol ?

i did the following test
Why did he disable the Group1Button2 and not Group1Button1

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