Its not about pushing the menu up or down. Only If you can hold shift space and make the mouse cursor hover over the previously selected tool, Only then the Menu stays otherwise not. It does not let you select in the first place. It slows down the workflow if one can't switch between the tools smoothly. When menu is activated in the viewport itself the problem persist. There is no time for you to select the tool from the menu. If you want to select different tool Press Shift Space twice consecutively, only then the tool menu waits for your selection. When you press Shift space twice these two steps happen

1. At first shift space selects the whatever tool that is present on the cursor and disappears.
2. When 2nd Shift Space pressed, As the mouse cursor did not move because of the first consecutive Shift space, Cursor is now hovering on the selected tool which happened to be selected because of the first shift space. Now it waits. But who wants to press shift space twice for the menu to wait. It does not even behave as a pie menu. It is a strange obvious bug.