Grr.. My own stupidity!
For some time now I have been using an
AeroPress to make my coffee, using rather than the disposable paper filters, a finely perforated stainless steel disc.
I had wondered why on earth it seemed to be getting harder and harder to press down on the plunger, and make my nice hot coffee.
Today I happened to look at the disc and discovered that roughly 95 to 99% of the perforations were blocked! After some heavy duty cleaning (seemed to go best when I used a steam cleaner to blast away at the disc), the holes are all open and coffee flows freely once more.