How do I release door lock on AEG Oko_lavamat?

I have an Oko_lavamat74689 update and the door would not open after a wash cycle (on Christmas Eve!). I drained from the drainage tube and opened the filter and removed some blockages. After re-assembly the door still would not open. I ran another short wash cycle, and at the end it gave the usual click to indicate the door was released and the door green light came on - but the door still would not open. I've taken the top off and can see what I think must be the door lock mechanism (I can't get my hand to it however, too tight) but not sure what to do next or how it works. Glad of any help. Thanks.