The lever on our la Pavoni EPC-8 sometimes (and more frequently as time goes on) fails to let water into the group, and the lever, when pressed down, just falls with no resistance and no water. Sometimes it has a little resistance and water in the last half of the press. What might be wrong? And can we fix it ourselves? We''re engineers, but can''t find a non-destructive way to get into the guts of it to see what is going on. We hate to start pulling O-rings out, possibly damaging them, unless we are pretty sure that is what needs to be done. Does anyone out there know the answer?