Negative Remaining Amount on Sales Order due to negative Deposit

Someone in our accounting department managed to post a negative deposit. I have a case open with support but nothing they’ve suggested is working. We need to be able to cancel this negative “Remaining Amount” out so we can post invoices to it. With this record the way that it is, any attempt to post further invoices to this result in a posting error about the order having a negative balance. Any one have any clues?