Thanks for the additional information, very helpful. The good news is that this payment didn't post to General Ledger with the 2875 date, instead it posted to 3/31/21. I can understand the transaction date (6/12/2875) not being desirable though. You can control transaction dates not differing from post dates by going to General Ledger > Business Rules > Transaction > and marking the box "Do not allow post dates to be different than transaction dates in other Blackbaud Systems."

Please see the attached screenshot of a posted payment with a payment date far outside of any open period.