I've had this problem for some time. Each time I make a Mars base, complete or not, Minecraft suddently decides to not allow me to play that map ever again. I've made two maps so far, both of them corrupted by Minecraft. The first one is stuck at the 'Downloading Terrain' screen while the Development Console repeteadly spams the following error loop: This error doesn't seems to appear at any other world, and is exclusive to this specific corrupted world. The second corrupted world manages to let me in, at least before crashing 2 seconds after, giving me a crash report that is both too long to fit here and that shouldn't go here and instead should be at the Bug Reports section. It says something about ticking tile entity and something related to Galacticraft 'Oxygen Pressure Protocol' and Universal Eletricity, and spams this error for a long time. So, yeah....anyone knows what is happening?