I think it will be difficult to reproduce it since I've done about a dozen flights and this is the first time it's happened, but I will try to do retrace my steps during my next flight and see if it happens again.
No I mean copying primary to secondary. But it didn't immediately freeze after doing that. I think I went back to the FPLN page and scrolled up and down a few times before everything froze up.
A few hours into a flight the aircraft completely froze up. The sim continued but every screen in the a310 was frozen and none of the buttons were working. I went into dev mode and took a screenshot of the error. I had just copied a secondary flight plan in the fmc right before this crash happened.