Help wanted with rendering quads while sharing a buffer

[Maix0]

code: github link
I have this code that should render each "decal" (a decal is a quad + texture), but only the last one is rendered.
i tried to reuse the buffer for the quad position and I think this is the main issue, but I don't really want to create a new buffer for each decal instance as they are created and destroyed each frame.

you can try my code by running cargo run --bin decal while in the repo root. Then type 5 and you should see two patterns on the screen next to each other making a rectangle (when it will work)