dataGrdid in ZEN

In Cache 2013.1.6.950.1 I have a ZEN dataGrid which works fine except if I use the mouse wheel to scroll through it.

If you use the mouse wheel (rather than the scroll bar) to scroll to the bottom of the grid and then click the checkbox against the bottom row it works the first time however if you then scroll back down the grid with the mouse wheel to the check box and uncheck it the check box will still be checked when you scroll back down to it and it only goes unchecked when you click in it a second time.  It works fine when the scroll bar is used. I have attached the code (cut down to show the problem) with some sample data. This code should be loaded in the USER namespace.