error code c9 on aeg oko_lavamat 86741?

AEG OKO_LAVAMAT L86741update got stuck at the end of a 30 degree cottons wash cycle and error code C9 is showing, with red flashing lights on the 'pre-wash' and 'rinse +' indicators. Before I call out an engineer I wanted to know what this means. I can't open the door to get my washing out. Have turned it off at the socket but error code comes back when I turn it on again.
Hope you can help