You mean after all this time you still haven't figured out how they do this?
It's related to time of the day.
Try running a set of rolls between midnight and 1am and then run a set of rolls between 1am and 2am, you will see.
Midnight to 1am comes out even or on a slight plus, 1am to 2am comes out on a gigantic loss.
(Other times of the day I don't know, I run the multiplyer exclusively midnight to 1am)
If you observe how your win/loss statistic evolves, you can even tell when the server switches, because the difference is visible within 10 or 20 rolls and since this happens every single day at the precise same time there can't be a coincidence.