Sorry I don't have my input displayed there.
Note: This only occurs on flag run challenges AB, BB, & CB. (The challenges that spawn tubes launch you in to indoor areas.)
But it's as simple as holding alt fire and then as you exit the tube pressing respawn before the teleport ball terminates when it automatically fires as you exit.
It's absolutely consistent in offline challenge selection and I was able to recreate it a couple times in online mode for these challenges as well though waiting for the rotation to get to one of these makes recreating it on video a little tedious but I will do so.