Due to a massive oversight, I decided it was a good idea to expand one of the structs that contain a lot of ship data like hull crew psi etc etc.

What I didn't realise is that this data is actually saved to file (god knows why tbh),  so, effectively, I was loading in more data than was originally saved, totally corrupting the save files.

All fixed now, yet another reason why we need to get a proper DB up and running.