Bosch Exxcel 8 filter cap

I can't see this answered in FAQs. I am trying to get the filter open on my Bosch Exxcel 8 / WAQ28461GB. I have checked various online resources but none of them seem to match our machine.

With the front panel off I can use the mini hose to drain but I can't get the filter open. In videos that I have found, the filter cap twists anti-clockwise for a couple of turns before pulling out easily. On ours, there is a moulded plastic tab at the top of the panel that stops the cap doing a full turn - so it goes almost all the way around, releasing water but it does not let me pull the filter out. It turns quite stiffly and there is no point where it feels like it should pull out. I know these things can get jammed but I have not been able to release anything. Grateful for any advice - not least, should it pull out when it is at its furthest point in the anti-clockwise turn?

So in the image, the black tab in the blue circle turns in the direction shown until it hits the white tab circled in red.

thanks, Andy