Wholesaler letting seller back out of deal

[Amanda Williams]

Happy New Year! So, I have an unusual situation and would love some insight or suggestions on how to move forward. I am under contract via an assignment contract (wholesale deal) to purchase a property. In my due diligence, I discovered that the parcel contains not only the duplex I thought I was originally purchasing, but also another small cottage. There is not enough land to subdivide based on minimum lot size requirements. Before I went under contract I asked the wholesaler about this based on the GIS and tax data and he said he checked with the seller and that the parcel only contained the duplex. (NOTE: The seller also owns the adjoining property and thought that the cottage was on that property along with another cottage). I was able to find where the seller originally purchased the property in 1985 and the survey that was attached that had the 2 parcels and the one that I am trying to purchase -- which clearly shows the cottage on the parcel. I informed the wholesaler that the property contains both the duplex and the cottage and that I would still like to purchase it. He spoke with the seller and the seller said he doesn't want to sell it if it contains the cottage. The wholesaler is not willing to force the seller to close --even though he is under contract to sell the entire parcel. This deal is a big one in that it would give me 3 STR's -- Major cashflow! My attorney says that I can force it because it is a legally binding document -- but I am not sure b/c it is an assignment contract, so wouldn't I essentially be forcing the wholesaler and burning a bridge???? HELP!! I don't want to be a nasty money hungry investor, but then again I feel like both the seller and the wholesaler should have understood what they were selling. Thoughts?