I've also been experiencing this bug on my game. Any time I load a new ship with molten salt or gas core reactors on board, they load fine the first time, but if I revert to launch or switch controls to the ship, the reactor flies off. The bug is expressing itself in a weirder way. I'm in the process of building a station above Duna using the USI Kolonization mod, and when I switch to it, the reactor/generator fly off, but oddly enough remain part of the ship, providing power and moving my camera view as they fly away. Happens %100 of the time in my current game, so can't get much done.