Catalog backup issues after 14.5 update

This is a known issue, usually caused by catalog corruption. I'm not sure why reverting solves it, perhaps the older version is a little less picky in this respect. First try if optimizing the catalog solves it. You can optimize the catalog without backing it up, so this should still work. If you still can't backup the catalog, then create a new catalog to see if you can backup that one. If you can, then this confirms it's your current catalog that has the problem.

In that case what you can try is this: Create a brand new catalog and choose 'File - Import from Another Catalog'. Select your old catalog to import. In the import dialog choose to import all photos, but do not move them. This will create an exact copy of your old catalog, but usually without the corruption. The only thing that won't come across is any publishing services you may have. You will have to recreate those. If you synced your catalog then you will have to enable sync for the new catalog. There are some reports that this could cause a problem. Here’s how to solve that: https://www.danhartfordphoto.com/blog/2025/1/lr026-fixing-sync-problems-caused-by-switching-the-sync-catalog