I run a (Export as a catalog) for all photographs on a weekly basis for backup purposes. With my current volume, the job takes close to 7 hours, I run it overnight, and upon completion have 3 folders, catalog, images, and previews. Since some previews are missing, the job usually lists (Missing previews) to be acknowledged as the last step before ending normally and updating the (Previous Export) total. For the past month, the process ends with what appears to be the (missing previews) screen but I get the message "Lightroom has stopped working". My backup drive has all of the usual 3 folders and everything appears to be OK except that the previous export number does not get updated. Has anyone experienced this and/or is there a fix for this? The fact that the export does not terminate normally makes me nervous.