Submitter reports that this issue has been introduced when the tab traversal behaviour changed for buttons in a radio group. Originally the buttons in the group were
traversable using TABS (with SPACE to activate the button) but now the cursor keys are used to cycle through the buttons. This was implemented in BasicRadioButtonUI class.
The changes also introduced a getFocusTransferBaseComponent() method which is trying to get the focus ancestor using the following:
Window container = SwingUtilities.getWindowAncestor(activeBtn);
This is failing when radio buttons are in one of our overview editors (which are Dockables where the focusCycleRoot is set to true and the focusCycleRoot is therefore not the Window).