Hey, so I found this issue that breaks the blueprint upgrade planners for express belts/undergrounds/splitters.
Basically, when editing a blueprint and you try to upgrade/downgrade from express belts, they get stuck not able to be changed.
Steps to reproduce:
1. Create a blueprint consisting of express belts/undergrounds/splitters.
2. Open the blueprint editor. Use the default upgrade planner to upgrade it to a turbo belt or downgrade to fast belt.
4. Now Upgrade/downgrade the belts back to express belts. You'll notice the belt speed changed to much faster visually, but the planner still shows them as being express belts. If you try to place this blueprint down as a ghost, it'll actually place an identical looking copy of an express belt but the entity is from Panglia rather than base game.
5. If you instead try to upgrade/downgrade the blueprint again it will fail and stay as an express belt (except the underground for some reason.) The blueprint is now broken and cannot be modified properly.