You should add one or two teleports in maps starting from hydra forest and so on. Specifically at the end of paths that deviated from the boss direction or half way through, it should unlock once you clear most of the enemies.

As I was playing again in a low level toon I noticed this problem in many maps, I was using a speed set so it was fine for me but this other guy coming along didn't have one so it was kinda sad XD