Only have one (not two) projects expansion icons. And it should change to show the current open/closed status.
It seems crazy (i.e. inconsistent and a waste of space and less easy to understand) to have two rather than just one icon for expanding and collapsing projects.
Maybe there was a sound technical reason for the way you have done it but... I suggest you either show the open icon (when projects are open) OR you should show the closed icon (when projects are closed) and the mouse-over should change in each case to say what happens why you click it.