[madeleinelevy]

There are no known issues with the make and model of my SSD card.

I understand the concept of working from a different drive. However there are more issues to be considered. One is that I don't have an internal hard drive and I would have to use an external one. Another would be that, well, what would we try to do here? If the aim is to duplicate the same conditions with a different drive, then I would have to make my Time Capsule back up the external hard drive rather than my computer. Considering that a few months elapsed between the first and the second lose of data, it make me a bit reluctant to go down this road.

So, for the moment I will check weekly for missing formats and make two backups. Time Capsule and Calibre will never run simultaneously again.

I will report back if it happens again under these new conditions.
Thanks everyone.