Okay, I know people may say this is because of power or antenna on 1.2, but for some reason, every time I get close to another one of my ships (i.e. attempt docking) with it. I can get about 20km away, and all of a sudden everything on the ship stops working.... permanently.
These are not large ships, and even the in game tutorial is doing this. When I was in career mode, I put everything in, made sure I had the antennas up, had several battery packs for my probe core and/or command module and the reaction wheels, as well as RCS. Even the RCS didn't work when I asked it to. The whole ship just went dead.
It's become very problematic for me to build stuff in space because of this. I've tried three types of control systems (mk1 pod, probodyne, and the mk1 lander pods). I tried looking it up and seeing if I was doing something wrong. I don't know because I'm a new player and got the game just a few days ago on steam.