22 year FBM seller. New to FBA. Strange sales slowdown issue.

Greetings. I’m hoping somebody might be able to help my little 22-year-old Amazon sales company with a mysterious sales issue we’re encountering.

An overview: We have 4,200 listings on Amazon. We decided to try FBA for the first time for a few reasons. Although we have 4,200 listings, most are mechanical parts for rare equipment, so approximately 4,000 of the listings sell once a month or even less, on average. About 190 listings sell more frequently, but not every day.

We have about 10 listings that sell every day, all year long.

We decided to start on FBA by sending two of these good moving ASINs to Prime. We chose two ASINs that sell about 5 units each per day minimum, consistently. Instead of converting the existing FBM two SKUs to FBA, we kept the FBM SKUs and created two new SKUs for sending these ASINs to FBA. We sent a quantity of 50 each to FBA.

These two products are tried and true. They have high demand and even have the Amazon’s Choice label on them now. In addition, we have a PPC campaign funneling traffic to these listings. To top it off, we have no real competition. A few sellers have duplicated our listings, but no one else is selling their listings Prime, and every other similar listing is far more expensive than our products. In fact, several of the other sellers are just drop-shipping our products from us at twice the price. We own the market on these products.

Despite all this, since the very day we sent these two products to FBA, sales have fallen off a cliff. We are now averaging one sale a day on each product.

Instead of more sales using FBA, FBA seems to have destroyed our sales.

Thanks ahead of time for any insights!