Iceman- I was/am using the latest PhysX at the time of the report. I ran update via nVidia Experience application to make sure. Said PhysX was already the latest version.
I reverted to an earlier point in the campaign. Played through without this issue happening again. Haven't had it happen since. I do have a bunch of addons installed now, but at the time of the original post, I did not have any installed.