For some reason all the worlds, even ones outside my domain, which I haven't touched are all Frigid with a -25% Habitability value.

There doesn't appear to be a way to remove it either. Using the command "effect set_frigid_subclass = no" just makes the world Arctic.

Terraforming (unmodded) does not remove this either.

EDIT: However if I use the 'play' command the worlds that once had "Frigid World" lose it. It seems to only appear when playing as my empire (play 1).