So the issue is that the mortgage company's report says that the house has needed some work in the past ; so are refusing to grant the mortgage , because they suspect the structural integrity of the
house ?
So if the buyer is really struck on the house , then it appears that they would need to commission a structural survey at their expense ( assuming the lender would accept it )
If the structural integrity is going to be suspect from other potential lenders , perhaps it might be an investment in you having your own independent structural survey done .
If the sale doesn't go ahead in this instance , perhaps it might be wise to await an offer from another potential buyer and see if their lender has the same issue
If they do then that might be the time to instruct your own structural survey