Why? Becouse you did an infinite loop, you have to disable changing position after touching portal with event like "Is overlaping & Touched_Orange=1 (some variable)"
Becouse it goes like this after touching one portal.
Player Touched Orange = Teleport to Blue
Player Touched Blue = Teleport to Orange
Edit: On second though it's not the Infinite loop thats locks the game (yet its still buggy) but the fact that you want to teleport the player into Block.