The mentioned behavior is encountered becuase of the initially hidden state and a logic in the RadEditor because of which the onParentNodeChanged() method is called automatically.
This method has an already logged bug and I suggest following the public feedback portal item
for a possible resolution.
Also, when it comes to programmatic showing and hiding of the Editor, it is recomended to use the repaint() method to fix layout issues. More about this is explained in this help article
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