ePro Fluid Req - account # changes unexpectedly when amount is changed

We are on Image 40, PT 8.59.03

Our Category Codes are populated with a placeholder account number that is not valid for transactions. We did this because there were too many Category Codes to populate and, as part of the conversion process, we were restructuring our chart of accounts.

When an Amount Only requisition is created and the account number chartfield is omitted on the Req Defaults page, the account number is defaulted from the Category Code. Budget Checking fails, as expected, because there is no budget for the invalid account.

After updating the account number and saving the change, if the amount is changed in the Checkout page, the account number reverts back to the account number on the Category Code. Budget Checking fails, unexpectedly, because the account number is not valid. User has no way of knowing the account number had changed because that value is buried on another page - three clicks away. Is this a bug or WAD?