Thanks for pointers Martin.
It appears no logs are being captured regards the recent random freezes as the only way to exit is force quit. I assume this kills any data the OSX logging would use. So still no clues yet on that.
I did however notice that a number of crashes which were recorded prior to my more recent freeze issue were related to Cubase 11 Video Diascope.
I have recently been experimenting with importing iPhone video files into Cubase. It appears therefore some instability with translation of those files, poss a frame rate issue 60 v 30, which is reported on video export. Id need to examine the input file side from the phone to see what Cubase is reading. My Project default usually set at 30 frame as setting at 60 appears to give problems at import.
Any pointers or ideas appreciated.