I can confirm that this is a bug in the framework which will be fixed in the next internal build.
Actually the problem starts from the Kendo Draggable component which does not allow focusing of input elements located inside the draggable object either. We will provide an 'ignore' option (for both Sortable and Draggable) which will accept a selector that specifies which items (children of the draggable container) will be ignored. Ignored items will be focus-able with the mouse. In other words you will be able to say ignore: "input" to make the inputs focus-able.
I hope the information will help. I will mark this thread as requires additional answer and will write you back when the next build is uploaded.
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