I think refractasnapshot is OK now.
I really do not know what happened but I re-installed the refractasnapshot and now I have made several snapshots with success.
I think it runs more consistently under command line...
I also prefer the command line progress bar.
When I had issues, the zenity 'progress' bar was driving me nuts
I also observe that it really is necessary to have all apps closed to avoid weird behaviour.
Keep up the great work!