I have been using the latest version of Tonfotos and am loving the metadata auto-embed feature for naming faces.  However, after a Windows reinstall (Windows was corrupted) I have experienced frequent crashing of Tonfotos while rescanning my 200,000+ images for faces.  When I restart, it comes up where I left off and apparently I don’t lose anything except the inconvenience of restarting the app.  The conditions when it happens are when I have at least one other photo editor (On1 Photoraw and/or ACDSee) running at the same time.  So, I suspect there is a correlation there.
I am just sharing this experience for your information - I am not expecting any special attention.  Thanks, Donny