One other thing with this/these damn safety relays, it says in the tech docs; DC: Connect terminal A2 (-) with the earthed side of the operating voltage. What the hell does that mean? And what is that terminal marked (-) with the ground symbol on it used for?

WHat worries me in all this is that the description for the PNOZ 1 says "earth faults are detected in the emergency stop circuit" whereas something like a PNOZ 4 does not say that. Could this be part of my problems? Very tempted to buy a PNOZ 4 instead but not until I have exhausted all avenues with these PNOZ 1's