Bosch WFK2801 washing machine - Error Code 06 / no action?

I have a Bosch WFK2801 front loading washing machine.

The unit is currently refusing to do anything (pump, spin,fill) just flashing up error code 06, along with the first 2 LEDs after around 30s of power up.

I *think* error 06 is a door lock problem.

When I apply power I can hear a click and the relay is engaging -- the door cannot be opened, so perhaps this is some kind of sensor problem.

But before I dismantle can anyone confirm or suggest any alternatives.

I've already done the usual cleanout of the waste trap, narrow pipe up from there, and the hex-shaped pipe from the pressure vessel to the pressure switch.

I've not yet cleaned out the pressure vessel.