Forum:Is there a build limit to Defenses in the C&C3 campaign?

Hi, so I'm playing the Croatia mission of the C&C3 GDI campaign right now, and found that after building 7 Guardian Cannons, the option seems to be dimmed out and I cant build any more. I couldnt find any info in-game or on the wiki so I'm wondering, is there a limit to how many defenses you can build in this game? If so, is it a limit to each type of defense (7 Guardian Cannons, 7 AA Batteries, etc),  or a limit to the number of defenses in general (i.e 20 turrets of any type total)? And is this limitation restricted to campaign/that one mission, so its not too easy or does it apply to multiplayer as well?

EDIT: I just tried selling some Guardian Cannons, but even after I sold ALL of them, the opton to build more is STILL dimmed out. Also I've found that after building an Airfield on this mission, the Armory becomes dimmed out, for some reason.

Is this some lkind of bug or does the game deliberately limit you like that?

- mresc