Could someone please post what this disappeared bit is supposed to look like? Looks legible to me when I screenshot and open in Preview on MacOS 15.6.1 (Firefox).

You are probably browsing with zoom, that seems to screw up the up rendering and makes the background and text look different. It should be just black&white random pixel noise for both background and foreground, without motion the text becomes invisible, as it blends with the background.