"This command disc has too many stages assigned"

The title explains the problem really. Tryna do the first satellite contract with that German guy, and I need to have 4 stages for that to work (If only 3, the payload would deploy before reaching orbit). However, when I then make 4 stages, which it allowed me to, and then tried to launch it, it said the same thing as the title. How do I fix this? Its quite annoying not being able to do what you need, and I don't understand how really lol. Help pls ;-;