The reason for the observed is the Kendo version used in the sample sent. The check
event is available starting from 2014.2.828 release of the widgets, while the version used in the Dojo is 2014.1.528.
By changing the Kendo version, you would be able to correctly handle the check
event and keep the required checkbox always checked. Here
you will find a modified version of the Dojo sent.
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