The described issue is already logged in our database for fixing. You could track its status by following this feedback portal item
Due to the complexity of this task I am unable to provide a time estimation for its resolution, although I can assure you that it is going to be resolved in one of the upcoming releases of the RadControls suite.
I can suggest to workaround the problem by setting a meta tag, which forces the IE browser to run on IE10 compatibility mode
Let me know if you need more information about this matter.
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