Basically I took home a brand-new 16 inch Macbook Pro, and a handful of times over the course of a few hours I saw graphical artifacts (random, tiny rectangles of pixels that would turn magenta, or green, or orange, etc. until that portion of the screen refreshed by scrolling or otherwise).

I returned that Macbook and ordered a new one. This time things seemed fine for the first 12 hours but then I started seeing the same kinds of artifacts, this time mostly on the menu bar (some were on the menu bar before).

I've noticed that while they aren't always on the Firefox window, they do at least sometimes correlate with things I'm doing in Firefox. Opening a new tab, visiting certain sites, etc. Turning off hardware acceleration in FF also seemed to have an effect (I'm trying Chromium now to see if they happen at all with Firefox closed).

I'd be shocked that two >$2k laptops in a row would have such an egregious hardware defect out of the box. Is it possible Firefox is the entire culprit? Or is it more likely that it just surfaces the underlying problem more often, by making greater use of the GPU?

Edit: This seems to be the same issue https://apple.stackexchange.com/questions/338319/red-pixels-on-mojave-dark-mode

Really I'm just trying to decide whether it's a software problem or whether I should exchange it again.