My version of BaseCamp updated itself today (1st time I'd used it since saving all my Tracks after PBP 2015).
It also replaced my entire "Collection" of Audax & Other Rides with a blank database. Some 6400 data waypoints/tracks/routes/etc.
Yes, I was near reduced to tears, having just logged a 2hour section of the Cheshire Cycleway Route 70 this morning (part of a longer term project to gpx the whole circular route) and transferred a series of rides from Mallorca off the eTrex into Basecamp.
1) There was no advice that the update would do this,
2) The update did not offer to backup any data automatically before or during this update install.
3) The updated version gave no help to find or re-install the previous database or collections.
My fault I guess, for not backing my Basecamp database/collections often enough. (I do keep 'exported' gpx file copies outside of Basecamp, along with all 'imported' gpx files from a variety of sources, such as Audax event files). But I was not wanting to spend hours re-building the Basecamp database of Collections, file-by-file again.
Fortunately, BaseCamp offered the opportunity to restore itself to a previous version, after a bit of digging around and, on the second attempt, returned to my Collections to their previous state. Phew!
Moral:
Do regularly backup/export Collections data outside of Basecamp (although it could not handle my 'Audax Routes' collection of 6400 items - being too big until I broke that down into smaller chunks) and do remember to do a Basecamp Backup before invoking any updates !