do you send your car back to the manufacturer when the fuel tank is empty or when it needs new window washer fluids? ;-)
The seals wear out, they are meant to be replaced every few years and thus the complexity of that task is kept very low. It really is a no brainer - half a dozen screws on the mask which have to lock back in tight, nothing else.
Mr Tsuji once wrote a nice article on how to analyse and fix a light leak: http://www.yt.cache.waseda.ac.jp/K88/adjust.html
The A12 and the Kiev magazines are mechanically so close to each other that you can use the A12 on a just very slightly modified Kiev88. Heck, they even share the same problems - film flatness and worn out seals.