I’m not seeing anything in the spreadsheet that might be contributing to it (such as if some IDs had a trailing space and other’s didn’t) but everything looks fine. I’m combining this with a similar bug report for African Carnivore Wildbook.
Since this bug isn’t likely to be fixed quickly, I’m going to recommend that you leave a single pair of duplicate individuals and you can manually resolve the remaining duplicate matches so that you can continue with your research. This way, there’s something for our devs to work from without leaving you stuck in your progress.