How can a Short Sales be rejected?

I have been doing short sales for about 3 years, I have seen a lot but I am still learning. I known that banks sometimes might denied a short sale in the following cases:

• 80/20 they can agree on how much each one is getting, sometimes the 2nd mortgage wants more than what the first mortgage is willing to approve.
• Contract price is too low or property is so ugly and has to many issues that no one is interested to pay what the bank has approved.
• Too many liens on the property and bank wants seller to pay for all or some of them and seller doesn't have the money to do it.
• Strategic short sale, the homeowner is comfortable making payments but because they are upside down they want to sell, but there is no real hardship.

This is the new one. Homeowner bough property with FHA loan back in 2007, got married and move out of the house and rented the property from 2008 to 2009. Husband loss his job and they moved back to the house in 2010. She was denied a loan modification, Wells Fargo send her a letter advising her to short sale the house. Then when I sent the concent for the bank to release information to me, they told me that FHA rejected the short sale because she used the house as a rental for a period of time and that she can't even do a deed in leiu.

We learn something new everyday.