Hopefully this is not too premature, but it looks like the answer was down to Norton 360. Despite switching off protection, adding exclusions, etc. I was unable to prove this early.
But going back into Norton logs, I could see some activity appearing in the Sandbox log.
Basically, I reset Norton settings, added exclusions (ADVANCED SECURITY -> ANTI VIRUS) for the App.exe and the VS .exe :
Program Files\Microsoft Visual Studio\2022\Professional\Common7\IDE*
And after a reboot, I have been able to debug as normal without any unexpected Code Exit.
Unless I add to this due to further issues, assume one of the above was the resolution for this. Thanks for all the suggestions!