I didn't realize you were using a later update. That has a new config.txt option: ALTMOD=ON|OFF. Added for users that don't have a Win key, old keyboards and Macs. So they can use the Alt key instead of Win. But that also disabled Ctrl+Alt+V if ALTMOD is not set to on. Probably I should re-enabled that key combination (even if ALTMOD=OFF, the default).