Search the App Store for "dead pixel" and download the tester. Put it on a red background and analyse the screen closely. You will find that your XS Max has at least 1 (but in most cases more than 1) dead pixels on the display (look extra closely because these screens have a huge pixel density). This started out with my first purchase of the XS Max but after purchasing an additional 9 phones I quickly have realised that this must be the case with all of them. It's a shame that Apple doesn't seem to have its OLED manufacturing up to scratch. Hopefully they get it right next year. I have returned all but one and I will keep it despite the dead pixels.