You've been on this platform for a very long time - I'm surprised you don't know how BIN and auctions work when combined. BINS are not reserves.

Setting an item with a high BIN and a low auction start price will always guarantee that buyers would rather go for an auction where they can potentially get the item for a far lower price than whatever you set as your BIN. As soon as the first bid is made, your BIN becomes irrelevant/falls away. Your current item has already had bids so no more BIN.

A better way to do it would be to either have a pure BIN item at the price you want, or an auction that starts at a higher opening price.

Since you're an intermittent seller, I do hope you've signed up for managed payments and been ID verified.