Anti-Competitive Featured Offer (Buybox)

I'm just curious if anyone has experienced this before, or have any advice on how I can get someone to understand from seller support (As when I explain, I'm borderline accused of being a liar or an idiot).

I have sold on Amazon for a number of years and have become accustom to the rough workings of the featured offer.

Although Amazon does not publish the specifics of the algorithm that make up the featured offer. We do know that the 'main' factors of this are price, fast delivery, and reviews/ratings.

For example, if I have the quickest delivery and a trusted high rating seller, If i price an item at £4.99, it is very unlikely that a comparable seller at £9.99 will sell the item. However if another similarly ranked seller was also priced at £4.99... the Buybox would 'rotate' somewhat - at the very least it would not be 100% to one seller.

This is what I've come to expect when selling items on Amazon, and although I'm well aware there are additional factors meaning it is never evenly split, sellers do get a rotation of sorts.

HOWEVER

I've recently came up against a particular seller, very similar in ratings etc... however when I sell the same items as this seller, I receive 0% of the buybox allocation. Even if its just me and them, same price and everything, they receive 100% featured offer allocation and I receive none.

I have raised this with Amazon and all they come back with is "You are eligible to featured on the Buybox". I am fully aware of this, however I feel as though the system is just not allocating me any time vs this seller.

I'm essentially told I'm ill informed and that the system would never not allocate the featured offer to me due to a seller... however I clearly know what I'm experiencing first hand... and have done for a number of months.. + Confirmed with data from Keepa etc.

Any ideas?