Imported image thumbnails are gone, SS can't seem to fix problem

Site URL: https://betsysharptile.com/

So as I write this, it's a couple days into SS's second round of "escalated review." No solution forthcoming yet.

When I do an image search of my own imported images, I only see about 2/3 of the thumbnails. The rest of the images that I previously uploaded just show up as blank squares and rectangles. However, if I click on one of those blank squares, I can add the actual photo behind it to whatever gallery or page I'm building. So, the uploaded photo is still there; I just can't see it until I add it to a page.

The lower-level SS helpers can see the problem on their end, but have no idea how to fix it. They escalated it before, and some higher-up person fixed it and said that a "broken thumbnail" had caused the entire problem. It stayed fixed for a few days, and then the same 1/3 of thumbnails vanished again.

Now I guess they're still trying to work on it.

So when I scroll through my imported photos, the most recent ones are fine. Then there's dozens that are blank, then several dozen that show up, then like 100 blank ones, and so on. There is nothing weird about the way I upload things.

If someone out there has a clue, maybe I can convey the info to whoever's trying to fix this at SS.