UiVelloSvg hidden by other absolutely positioned UI Nodes

I'm implementing a chess GUI and trying to render piece images with `bevy_vello`. It appears that the zIndex / visibility logic differs between `UiVelloSvg` and `ImageNode` from Bevy. I have a `Node` for the full size of the chess board and then many absolutely positioned nodes for the squares. The pieces are then also absolutely positioned nodes on top of that. <img width="801" height="658" alt="Image" src="https://github.com/user-attachments/assets/40fefa14-01c0-4864-a33d-ca904e5f7bed" /> Here you can see that with `UiVelloSvg` other UI nodes at the same position are always rendered _above_ the piece images (in this case the move highlights, board hidden so you can see at least some other pieces). I already tried explicitly configuring `ZIndex` and `GlobalZIndex` without success, which I thought were supported with #164. Is there something I can do to make this setup work?