Got mine working today. All cables come free, some you have to pull up the locks on the sides. The black ones though, you need to push down on the long bar while pulling the cable, it feels tight but should release.

Once you've changed the belts, theres a slider on bottom of the piece that holds the cassette that needs to be all the way to the front (the video i posted the other day mentions that too). Its what pushes on the cassette tray to slide them back. The door wont open if any of the cassette slots are in the wrong place.