I was using Mac OS Catalina (vs 10.15) at the time. If this happened, the project would be severely damaged, so I'd have to go back to the most recently auto saved project and try again. It might have got ten minutes or so along the sequence before the Macbook Pro graphics processor would suddenly give up followed immediately by the whole Mac crash shut down. In my case I now realise that my Macbook Pro processors were over heating when pushed to render OR export un-rendered UHD ProRes HQ sequences that contained warp stabilizer, LUT and colour grade.
