Do I have rights if my pre approval letter was not correct by no fault of my own?

We contacted a lender, applied for a home loan, and because my fiance had some student loan debt, it was suggested that I be the only one on the loan. I provided all my additional info, and received a pre approval (not pre qualified) letter stating I was approved for $250,000 without having my fiance on the loan. About a month after receiving this letter and house hunting, we decided to go with a brand new home for $221,750. After we gave our earnest money and signed a real estate contract on the new home, our lender told me that they made a mistake, and is requiring me to do a lot of extra things to now be approved. I asked what the mistake was and if I am still approved for $250,000, but I still have not received a straight answer, but was assured that I'll be OK if I take care of the new extra requirements. And when I tell them I can take care of it, a new issue pops up. As a consumer and a buyer, do I have any rights against the lender for messing up our pre approval?