Medicare Coverage for Exams following Mastectomy

Hello,
I'm new to this group. 21 years ago this month (January 2026) I was diagnosed with DCIS in both breasts. I had a bilateral mastectomy with reconstruction. I am well!
For the first 14 years I had checkups (every 1-2 years) with the same breast plastic surgeon to ensure the integrity of the implants. Starting with year 14 my insurance has been Medicare and BCBS and the exams were fully covered. Then I moved out of state. After locating a new plastic surgeon my next checkup was at year 18. The exam was denied by Medicare. After escalating to the executives of the medical system, the claim was recoded and paid by Medicare. It took 2 months to correct. The next year the exam claim was processed by Medicare without issues. Now, in year 20 (2025), Medicare again denied the latest exam claim. The provider's financial and billing teams revised the claim coding and resubmitted for processing. 4+ months after the exam I have again been told that Medicare denied the claim a 2nd time, as has BCBS. I have not received anything nor can I see on my Medicare account anything about the denial reason for the revised claim. I only have an email from the provider's practice administrator. (The first 2025 Medicare claim denial indicated it was a "routine" exam and therefore not covered.)
Has anyone else experienced issues with Medicare denials after reconstructive surgery? If so, I could use your advice on how to resolve this (other than moving back my home state and being cared for by my original surgical team).