Suddenly, about half of my keyword tags (about 300) are set to zero (0). As I didn't notice this until recently, I have made updates to my catalog (edits, new keywording, new imports). Retagging each photograph is not really an option, given how many are in my catalog.
Is there a solution for restoring these empty keywords? Suggestions for how to prevent this problem from occurring again? Thanks for any advice.
Specs: LR 5.7 on a Mac running OSX 10.2.2
Potential cause: The cause of the problem is unclear, as it happened shortly after both upgrading LR and switching to a new external HD