Color/tangent Wave bug or oversite?

I have mapped 'Toggle playback' to a function key. I use this in conjunction with 'Mark in' and 'Mark out' to 'loop playback' over a scene change. So when I have finished this 'loop playback' I need to go back to full timeline playback.
But I have noticed that the GUI does not respond to the key command until I move my mouse. So in essence it still shows the 'Mark in' and 'Mark out' indicators even after the 'Toggle playback' function key has been pressed, then with a slight mouse movement those markers then disappear.
Under normal 'mouse to menu 'Toggle playback' clicking (not using the Wave panel) this would not be a problem, obviously because the mouse was being moved when selecting the menu item.
Can someone else confirm this behaviour?

Baz

What would I do without the 'UNDO' button!!!!