Temporarily damaged credit, need lender

[Alex T.]

I'm in the process of buying a triplex, where I'd be living in one of the units. Purchase price of $1.2 mil, I have W-2 + rental income sufficient for the loan, and I'm hoping to do 20% down, but may be able to do 25% (I would prefer not to). This would typically be a conventional jumbo loan, but while applying for one I noticed a problem I was not aware of earlier. Basically, last year I refinanced one of my existing properties, and a few months later I switched payments to autopay. I found out 2 months later that their autopay system was not actually charging my account (something they neglected to mention was that their autopay does not kick in until 2 months after, and in hindsight I should have double-checked it rather than trusting their autopay). I immediately made the account current, but they still dinged me with a 60-day delinquency and my credit score dropped from over 800 to 683.

I'm trying to get it fixed (was not aware that this got reported until I got the house under agreement, since earlier phone conversation this year said otherwise). I'm having a tough time getting their servicing department to look into this and reading more similar cases online I'm realizing that lenders are reluctant to issue corrections and I may be stuck with this problem. In the meantime, my credit score has only recovered to 699 so far (this happened only 4 months ago) and I need to close on this purchase I have under agreement. It seems like once your score falls below 700, most lenders don't want to touch you with a 10-foot pole, even if you had a spotless credit beforehand and all your other assets are in order. I also did not realize that a single item can hurt the credit this bad. 

I'm guessing I'm not the first or last person in this situation. Is there a lender that offers conventional (or similar) loans to people in my situation? I'm ok with higher interest rate as long as it's within reason, or a different type of loan I can refinance out of once my credit is repaired (either via dispute or by waiting for my credit to build itself back up). Seller has a loan too, I've asked them if they'd consider seller financing, they're still thinking about it.