My edits don't seem to have made it; I don't see them.

There's an old electronics troubleshooting trick I mentioned in the edit:  Start in the middle.  That tells you which half of the circuitry is failing.  Once you know that, go in the middle of that and see which half the failure is.  If you have a single item with a texture that is failing out of 64 items, you can narrow it down to two choices in only five tries.  Much better than turning off items and then adding them back in one by one.

Again, my apologies for trying to tell the experts how to find the problem. I'm good at playing Captain Hindsight, I'm afraid.