I had messed up my index array creation, but once that was fixed the
textures worked well other than a lot of pixels are shades of grey due
to being in the top or bottom color map range.
I don't really know why (I need to do some research), but this fixes the
lockups when accessing the matrices UBO. It has made a mess of my
carefully designed uniform binding layout, so I hope I can get bound
descriptor sets working the way I want, but I really need to progress on
the rest of the project.