The error:
Cannot measure distance between <world1> and <world2>
Usually happens when a skill is locked in on a player and tries to damage them after they die and respawn. It's trying to calculate the distance to see if they are within range of the skill.
the target player variable probably needs to be canceled upon death to prevent this from happening. It really only shows up if your players die in one world and respawn in another. Or a check added to each skill that cancels the skill if the players are in different worlds.