SOLVED
I just deleted every part apart from the main one and then clicked 'undo' till everything was back. Now it all works as expected. I didn't actually do anything apart from delete and undo! Weird..

Im just starting out trying to learn the fundamentals of Solidworks and using a Spacemouse for the first time and I'm having a weird problem. I have 4 parts that are all working well with the Spacemouse - everything moves like you'd expect it to with no issues but when I combine them into an assembl...