4.7p3 BP Asset thumbnail issues

I have an asset that does a set material in its construction script to turn it yellow

So that part is all good!

But wait! Out in the project, the thumbnail for the cube always renders as white, never yellow. Hmmm…
I know, I’ll just update the thumbnail out in the project view under Asset Actions!

Weird, the “Capture Thumbnail” menu item doesn’t appear for this blueprint?? I’ve noticed it’s there for about half of my blueprints and not for the other, but it also seems to be totally random why that is.

Ideally it would make the thumbnail yellow to start with, but if that’s not going to happen, why can’t I capture a new one? I also tried the “View Options” “Thumbnail Edit Mode” but it will only show it as white.