In QML when a combobox is located near the border of the screen it does not open the dropdown menu when clicking on it.
This can be easily reproduced when the combobox is anchored to the bottom of the app window and the app is in full screen.
On some machine is it not reproducible otherwise reproducible in general:
This issue appears (at least) on these 2 devices :
MacBook Pro (Retina, 13-inch, Early 2015) under 10.12
Imac (5K, 27 inch, Late 2014) under 10.11.6
MacPro (late 2013) under 10.12
The bug does seem to appear on this setup :
MacBook Pro (Retina, 15 inch, Mid 2015) under 10.11.6
Attached is the example: