Odd keyboard arrow behavior

Not sure if desired behavior, but NOT intuitive.

With display in grid square view.

1. select a stack

2. select the stack number icon to expand the miniture filmstrip on the bottom for the images in the stack

3. use the mouse to select an image in the stack filmstrip

4. use left/right arrow to flip between a images in the filmstrip

5. use the mouse to select another image in the grid square which is not part of the stack

6. try using the arrows to move between selected images.

Result: Only the left/right arrorws work. The stack filmstrip is still active.

Personally, I would expect when in step 5 that the stack filmstrip would close. In any case, not having the up/down arrows work is a little weird.