Shift+Space and Ctrl+Space shortcuts intermittently working

Strangely, my excel wasn't responding when using the Left Shift+Spacebar or Left Ctrl+Spacebar shortcuts for selecting an entire row/column. But, then I tried the RightShift+Spacebar and it worked. From then on, the shortcut worked even when using LeftShift+Spacebar.

Unfortunately, no matter if I'm using left or right Ctrl+Spacebar, the shortcut does not work. In fact, once I try to use Ctrl+Spacebar, the Shift+Spacebar shortcut suddenly stops working until I mess around with it a few more times.

I should note that other ctrl shortcuts like ctrl+9 and ctrl+0 work perfectly.

Am I taking crazy pills??