A handy tip that I learnt is when you are importing from a data file, only import one of the following to start: EID, Society ID (if all the animals have one), Primary Id
By importing one key identifier Stockbook will provide an error report without importing all the data too. Then once I was happy with how the data was coming into Stockbook with out leaving gasps in the database, I imported the animal names and the rest of the data.