2 player local game. Playing Windswept Peaks. 
One player some how got stuck on this part of the map on a building top.  Then the other player was blown off the side and respawned next to the stuck player. 

Once there, we could not do anything. You can't roll off the side. You can't climb out. Return to checkpoint was not available. No enemies to kill you so you can respawn elsewhere. 
We even tried to log the 2nd player off and rejoin the game with the first player standing in different spots, hoping that player 2 might respawn on the upper block. No luck. 

We tooled around for a while and eventually had to just quite and return to camp.