Possible fix
I was having the same issue for a while. I noticed that if I tried to add a dependency to an already half completed map it would muck everything up and all of my alterations and even my CREATED units would default to their original values...and I would have to go through and alter them again.
but as for adding a dependency such as the Campaign units, when you do it, its best to use the little arrows on the dependency screen to place the campaign file on top of the melee and mod ones, it becomes more important and the units you are seeking to use and edit will show up.