Perfect sneak glitch
I just found a nice glitch!
At the last mission when you have to reach the Bar of the Eiffel Tower, just take the elevators until the last floor, then go back to the ground with the elevators (do not complete the mission, just go as far as you can with the elevators, it should shut down the Lv5 alarm)
Now you can go anywhere, the Nazis won't notice you and won't set alarms, even if you kill them in front of others!
The bad thing is there won't be any civilians either, so you'll have to find cars, or call the Resistance for help in order to make them bring you one.
Nice for sneak killing generals and mop up some free missions as well