Is there a scenario where if AMZN is the only FBA seller, it is impossible to win Buybox?

Hello, Some background to my question: I have a healthy account, 10+ years, no claims, account in good standing, etc… Basically no reason to be treated any less than another seller.

Every now and then I encounter a listing where AMZN is the only FBA seller for a third party product which I happen to have, and go ahead and send it into FBA. After a few weeks of sitting alongside AMZN at their BuyBox price and not getting the Buybox even once, I will drop the price and still not get the BuyBox.

However, most of the time AMZN will share the Buybox even if my price is above theirs. So I’m wondering if besides for Amazon Basics products, if there is a scenario where Amazon will simply not give up the BuyBox under any circumstances. Has anyone seen this before?