Stiff door on Tecnik dishwaher?

I have an inbuilt Tecnik dishwasher, model no. FD8312 which is just under 3 years old. It's front loading door has become quite stiff and at about 2/3rd open, it gives a 'clunking' noise from the right hand hinge as it seems to be forcing its way open. Any ideas or if not, how do I get access to the hinging mechanism. Thanks in anticipation.

Tim Cripps