An update:
On the advice of one of the Adobe folks,we created and opened a new Ppro project and under The Window dropdown menu, went to the Workspace submenu and unchecked “Import Workspace from Projects”.
We closed that empty project and opened a project that had previously crashed repeatedly, and it opened normally.
We will likely trash Preferences for the user. Just this one change corrected the issue, but it suggests issues with user Prefs, for sure.