Please see the video below:
Drag with the mouse to select multiple objects. Then Shift-click on one object to deselect it. The result: the Shift-clicked object is the only one selected.
Select multiple objects by Shift-clicking on each. Then use Shift-click again to deselect or reselect any of them. The results are unpredictable.
PS: works as expected in 1.7.3
Recording-9.mp4