- 6 players but can't upgrade to the final shortcut: the more players who pass an upgrade stage at one time the better, one "waiting zone" isn't limited to just one player at a time.

- returning from the track through a teleporter smashes me into a wall: partly intentional, you can only return through the currently "activated" shortcut portal

- i'm not respawning at the route selector: you've likely already been on the track, the shortcut can only lead to/from one place at a time, and the track has checkpoints to stop anyone from directly returning to the upgrade lane when they want.