The lenders are very slow to respond and when there are more than one lien holder, the lenders not in first position can be very reluctant to give up their position. Even after all lien holders agree on a sale price, the seller can back out of the transaction. In the State of California it is very important for the seller to involve an attorney and a CPA because of the possible Tax consequences if the loan(s) on the property are not Purchase Money (the loan taken out during the original purchase of the property.
It is very unfortunate that the Short Sale process is so difficult. Ultimately lenders receive less money if the property goes into foreclosure instead of a short sale.