Pictures distorted and pink

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I should have looked at the screenshot more carefully. The translated error message:

That means the file is missing from the location where LR thinks it should be. If you go to Library Grid view, you'll see an "!" in the upper-right corner of the thumbnail. See:

https://www.lightroomqueen.com/lightroom-photos-missing-fix/ 

Building on dj_paige's reply, it's very possible you're tripping over a known graphics-driver bug in Mac OS. Please do the LR menu command Help > System Info and copy/paste the entire contents here so we can see exactly which versions of hardware and software LR thinks you're running and important LR options that are set.