Buy Box eligibility lost with no reason with perfect metrics

Same thing happened last week and Buy Box eligibility came back ON in 1 day for no reason. My metrics are perfect with 100% feedback ratio. I have been a book seller for 13 years and I am all FBM. No FBA.

I clicked on help and let Amazon called me. Talked to the customer rep and as expected he said BB is something they can not handle and he has to forward the request to the team specialized in BB. I insisted on talking to Captive Team but he said there is no need.

Any suggestions?