Oh, that’s actually a pretty simple solution. 
But even here there is some problem. If I use the mouse wheel when mouse cursor is on the decButton or incButton of DirectScrolledFrame, the thumb always moves in one direction, which seems like the buttons are triggered instead. And doesn’t seem to work when mouse cursor is on the thumb itself.
Unrelated to my new problem, I still think something like
DirectScrolledFrame.bind(DGG.WHEEL)would be cleaner and more convenient as people wouldn’t have to worry of writing the appropriate code in their camera manager classes and worrying about setting “suppressMouse” to False in their GUI objects.
I know that there is a list of more important stuff in the schedule, so maybe I could post this in launchpad for future reference, if you agree.