I have experienced AA crew getting hurt on the surface when the AA gun has been damaged but the crew aren't on station.
I have had more than one case of a non-repairable but only slightly damaged deck gun.
I haven't had an issue with being unable to repair the AA guns but a number of posters have reported it so I have listed it in my rather long but thrilling (OK ok not thrilling) bug list.
By the way - I could do with all the feedback I can get, latest version of the list here:
http://www.subsim.com/radioroom/show...112193&page=16