After looking over my USB Hub schematic, I found the likely culprit:

The USB Hub chip has an NRESET pin. It's expected to be low during startup, and then go high when the power is stable (and for the rest of the runtime). It also has some requirements for how long it has to be low for. I googled this sort of pin setup and got a lot of info about how a simple RC network isn't ideal, how it doesn't handle short blips in the power supply as well as it should, etc. so I put off designing that circuit. I meant to investigate whether there was a cheap and simple IC I could use that handled all the edge cases.

Then I forgot.

So on my actual board, that pin is just floating.

I told my daughter that the next round of boards would be for a thing I'm making for her. So I need to update this schematic, but it'll be a bit before I can order a new board. I will probably try to solder some wires to pins and see if I can bodge a test out of this. I'm annoyed, but at least it's not a mystery anymore. If the failure was unknown, I would have no way to move forward!

As part of hooking this board up I discovered how much I hate crimping my own cables. Realistically, it's going to happen, but I might change the type of connectors based entirely on which ones are less annoying to crimp. We'll have to revisit that later.

What I want to do is move forward on the mechanical aspects. The problem is I can't commit to a size. I have an Ender 3 v2 right now. It's this weird middle ground. It's not big enough to print everything I've ever wanted to print (but it prints 90% of things just fine size-size). It's too big to be all that fast (especially as a bed slinger). But do I go small and ultra-fast or big for my custom-built one?

I think the right answer is big for the first one, then make another to be small and fast. My reasoning is that the big one opens up new possibilities, the fast one just makes the same kind of things faster.

I have what I think is an innovative idea for the walls of the printer and the enclosure. The math hasn't worked out yet, I need to figure out how to make it work. That's my goal for today: make the math work for my walls. And start uploading some pictures to this project. And ideally even start publishing info on the wall thing. Depends on if I manage to figure it out.