Are sure you are being hit with Double lates? Be specific how many actual lates are there. 2 - 30 day lates? This First mortgage should say Closed transfer to new Servicer and should reflect the exact dates each 30 day lates happened. The new Servicer is responsible for reporting the entire history of any loan they service also including the late pays but FICO handles these as the same loan and Not NEW debt so the system knows you only really have the one loan and the reported 2 past due payments. To be clear both servicers should be reporting the exact same, the exact lates and dates of those lates. The only difference in the reporting should be the 1st Servicer should reflect Closed & transferred to new Servicer. In the record it is very clear this one and the same loan that has been transferred to a new Servicer. Another thing you can do is enter a Consumer Statement into the record.
That is terrible i am going through the same thing. A short sale done in 2016. Banks sold the loan when it was already late maybe one or two months and new bank reported also late 120+ until short sale was concluded. So unfortunately same loan reported twice. I am still trying to figure who i should write a Gw letter first! I hope you resolve you situation soon. 🙏