Hey,
Here is the solution: go into the function called Trace teleport destination (1st image), in the Break hit result find the Normal, break it into floats and check for the Z to be positive. If it’s negative it points downwards so make the IsCeiling boolean true (of course create the boolean first). Also lower the Project Nav Extends variable (100 worked for me). This will avoid accidental picking the next floor. Now go to the MotionControllerPawn (2nd image), check if the IsCeiling variable is true, if yes, set IsTeleporting false and disable the teleporter.
Regards,
Fisher