Sometimes the Firefly III CSV importer will create duplicate transactions, despite being told not to. This is pretty annoying so please open a ticket when this happens and let me know why Firefly III didn't detect a duplicate. I can use this information to fine-tune the duplication process.
Use the debug view to see why a transaction is imported, despite being a duplicate of another transaction.
Open both transactions in different tabs of your browser. Notice how the URL is something like this:
Change the work "show" in the URL to "debug":
If you do this for both transactions you will end up with a specific JSON variant of the transaction.
Send it to me or compare it yourself to see the differences between two seemingly equal transactions.
updated_atfields are not used in the comparison by Firefly III.
original_sourceare not used in the comparison by Firefly III.
Please open a ticket on GitHub.