Invisible

Corrected 3rd image - apparently I managed to take the same screenshot twice the first time around.

I'm wanting to remove the requirement to have a "Wide Barbette (Very Small)" fitted on my ships in order to put any other kind of Barbette on them. It's probably a bug, but it's an annoying one and I'd like to fix it myself if I can. How would I go about doing that? Thanks in advance for any help :)