If you let them in, good luck getting them out — or out with your house in the same condition.

x2 on asking for the denial letter. For all you know they had a loan and then asked for lower rates more in line with what is currently available at the lowest level and they just backed out in hopes they’ll get lower rates elsewhere.

I’m no expert on this, but I would get it back on the market and let them know you hope they’re the ones who are able to close on it.