I would also tell him he has until X to address this issue or you will and will bill him not only for the fix but the damages. 

Maybe the flippers addressed some of these problems or maybe they encountered them and now have decided to bail on the hold.

Most lenders are hesitant to give you financing with no skin in the game for the first deal. 

Following.I print, address, and mail my own.  

To get the deal, I got a list of homes in two separate cities all older than 1990 and sent out 16,000 "We Buy Houses" postcards to the addresses - roughly $6,000 all-in.

And that is actually a  price for volume printing .. which works... it still becomes a  2 step process..As well you would need to make sure that they are individually addressed.

Do you have any troubleshooting or tuning tips to diagnose and address why some of the registers are having weak to no air flow?

.#2 - I hope every IRA investor reaches out and writes a letter to address this. likely not going to be thought out and still won’t affect their target, which means those below or on the fringe will be cut out from investing. 

Whats the address?

I'll PM you the address so you can start to do some due diligence.