When I'm editing an item that contains a Choice control that is placed inside a panel, the value doesn't get updated unless the first option is selected. 

The Choice control is connected to a SharePoint Choice column with the option 'Checkboxes (allow multiple selections)', it is then placed inside a panel.  I also give it a Name of 'MyChoices'

It doesn't matter what the choices are, could be "One, Two, Three, Four, Five"

I've also placed a Calculated Value control on the form with the formula referencing the Named control 'MyChoices' so I could see what the value that I've selected was (this was just for debugging).

On new items, it doesn't matter what checkboxes I select, I can see the calculated value field updating with each selection/deselection.  However when I go back and edit existing items, when I select new checkboxes (or unselect checkboxes), the calculated value field does not update.  It is only when I select/deselect the very first checkbox that it recalculates.

For example, if i selected "One", "Three", "Five" and saved, when I go back and edit that item and select "Two" and "Four", the value of the calculated control will still show "lOne,Three,Five]" even though all five checkboxes are selected.  When I uncheck the first box ("One"), the value updates and displays "dTwo,Three,Four,Five]".  If I go and uncheck "Four" and "Five", the value doesn't update again until I've re-selected the "One" at which time the value updates to "pOne,Two,Three]"

Everything works when I move that Choice control back onto the main form (i.e. not inside any panels), but that would screw with the design of the form :/