It's not well known but Svetlana got a transfer to Moscow and made the Zorki 4 that fell to bits in my hands two weeks ago. Still, I kept the lens, the case and the back.
I own FSU cameras of various vintages and all respond well to surgery. The more I use them the more I have respect for them. Sturdy and well made - problems are often caused by poor repairs. Jocko's advice is very sound. Overhaul doesn't cost much and the camera will function well for years. They're like Morris Minor cars!