Editing Transaction, "Number has already been taken"

version 3.0.11

Every time I edit and attempt to save a transaction - for example, after editing the date a bill was paid - I get the following error on the Transaction Number:
"The number has already been taken."

Completely stuck, my only recourse is to modify the database

Problem traced! It's a result, again, of a failed upgrade.

Database has duplicate "TRA-" numbers EVERYWHERE. It's as if 3.0.11 didn't even look at the data from v2 before creating new transactions.

The upgrade engine *seriously* needs data verification/cleaning functionality. I haven't had a single upgrade work, ever. And now I have a messed up database to go with it. I'm literally terrified to do an upgrade because it costs me months of cleaning.

Having said all that, I have no idea how to fix this other than to manually modify literally thousands of records in the database.

Update: Upon investigating further, the problem is database but it's even dumber than I thought. The duplicates appear when there's a TRAnsfer *and* and TRAnsaction. It's not happening all the time. The error in the Transaction page is referencing a Transfer, because they both start with TRA. Obviously, the "Number" column of the _transactions table needs to have data that separates a transfer from a transaction. Perhaps TRF for transfer and TRN for Transaction.