All gravity blocks float above the void and do not fall down. All y coordinates above 64 work normally. I did realize how scaffolding worked here, it behaves strangely.

STEPS TO REMAKE:

1. Add scaffolding next to an already existing solid block or use commands.
2. Build upwards using scaffolding.
3. Try to fly/walk through it; it is transparent and no blocks stop your fall. It is also apparent how the scaffolding sound plays whilst you fall through.
4. Build horizontally. The scaffolding block above and below the block you selected should disappear.
5. Break the bottommost scaffolding. Place a scaffolding underneath. The top scaffolding should raise, and a scaffolding should fall into the void.