I got a response from the record company today. Surprisingly informative:
So it's not just a few bad pressings, but all pressings due to the quality of the source material. Raul and Atmasphere, would you like to retract your responses? :)
Three different plates were cut trying to get it right at the factory, but the noise on the recording remained present because the recordings were mastered at a low volume; the version that was released was the best that they could get without having it completely remastered. It was approved by all parties involved and thus was released.
So it's not just a few bad pressings, but all pressings due to the quality of the source material. Raul and Atmasphere, would you like to retract your responses? :)