Corrosion on slide - Killer Innovations Velocity V1 Sig P365 Standard Pistol Slide

I bought this slide a little over a year ago, and had to send it back because of corrosion. They use a third party to coat their slides so I had to wait a little longer. After it was recoated, the same thing happened. I would have tried to send it back again, but I had to have a local shop fix the sights that were extremely messed up after receiving it back. I had to pay for that, by the way. It is unfortunate, because if the slide didn't have that corrosion, it would have been perfect. For reference, this is DLC coated and has Radian parts that are also DLC coated. The radian parts are immaculate.