You should experiment with the trigger_push's strength a bit in your map. In this one 1000 was too low, you could reach the ground. When you are on the ground the push seem to have no affect, only when you are in mid air. In much dipper pits 1000 would be perfect, by jumping you can reach places down in the pit and afterward jump back when you are done with them.
If the trigger_push's strength is below 1000 it doesn't seem to affect the player in the vertical vector only horizantaly..