This shortcut suddenly doesn't work anymore. Don't know why. 
Affected input device (e.g. MacBook Trackpad, Magic Mouse/Trackpad, Touch Bar, etc.):
MacBook Pro 2018
Describe the bug
It's still not working. 
For this specific use case, try to enable the "Differentiate between left and right modifier keys" option:
It works, thanks! 
It stopped working again. And now enabling or disabling "Differentiate..." doesn't do anything.