I've had contact with support regarding these crashes, which happen randomly but especially when going to and fro between the song and the project. Despite excellent help from Lawrence, I still haven't resolved this. It did not happen in earlier versions. I have made many changes including putting all my plugins on one path and various PC optimisations - a small improvement but still it's being troublesome. Very embarrassing in front of clients.
There is also a long delay when move from the song to the project. S1 is reported as not responding in taskmanager when this happens.
I am using a fast Dell with lots of memory and an SSD.