Arrow keys for moving cursor in an edittext (grouped vs. not-grouped)

If I put an edittext inside a group (or a panel)  like in the code given, I can no longer move the cursor with arrow keys, whereas if I parent it to the window, it works. Any ideas how I could get them working inside a group too? Is there some setup thing or a magical property somewhere I'm missing?

(Using latest Photoshop CC 2015)

var win = new Window("dialog", "hello world");

var text_a = win.add("edittext", undefined, undefined, { multiline : true, readonly : false });
text_a.preferredSize = [ 600, 80 ];

var group = win.add("group"); // Doesn't work with panel either
var text_b = group.add("edittext", undefined, undefined, { multiline : true, readonly : false });
text_b.preferredSize = [ 600, 80 ];

win.show();