Double Title

My name is Henry.  I will be grateful if someone can help me. I mortgage my property in 2021. My conveyancing solicitors did their searches and confirmed that everything was fine. Later, I received my title deeds from the land registry. In September 2023, I put the property on for sale, and not long i found a buyer, and we started the process of paperwork.  My solicitor agreed 22 December 2023 for exchange of contracts and later on this same he call me and told me that unfortunately exchange of contracts will not be possible because the lender has found that there's another title for the same property. The exchange of contracts didn't work because of the double title of adjoining land with a different title. The original names in this second title sold this property in 2017 to the person who I bought the property in 2021. They wasn't any issues at the time I bought the property. What can I do. Thanks for your response. 

Hi Henry - it reads as if the second title should have also been transferred back in 2017 and then again when you bought. But it wasn't. If so then you/your solicitor will need to trace the still registered owner and ask them to transfer it now