You could have a secondary step in-between each teleporter, like so: Teleporter → trigger → teleporter. When someone enters the teleporter, the trigger connected to the one that they went to should deactivate, so no one else can enter. This has the effect of causing a “misfire” where nothing happens, which could be solved with a loop somewhere. The whole setup would be like so: Button → trigger (RNG block code) ->(via channel) trigger (deactivates if someone teleports there) → teleporter.
Place walls covering all the teleporters that individually activate once someone enters a teleporter. Once all the teleporters have been taken, deactivate all the walls.