Listing looses featred offer after order with large quanity of units

Hello,

I am brand owner, only seller, FBM, and listings from time to time looses featured offer. I think it happens after order with 20+ quanities. Because I use FBM and I use shipping template that creates shipping costs per order + per weight. It is created in a way to reflect real life shipping contract - the more units in shipment the cheaper the shipping price per unit.

Could amazon's algorithm calculate average order value of unit, and as these large unit orders come in, it makes amazon think I have to sell listing at lower price?

But that is complete madness!!! I cant sell the item for lower price. Item costs 65€ and if I lower it to 62€ I get featured offer. But I need to sell it at 65€...

Support instantly ignores me as soon as they see words "featured offer". They just copy paste usual message about not disclosing anything about featred offer.

What can I do to fix this? I cant keep lowering price! I went from 65€ to 62€, now again 62€ lost featred offer. And I need to lower it even more?? And this happens only on my main markets DE and FR, other markets dont lose featured offer...