[JavaBrewer]

Yeah I'm no expert either, but the tech said that the machine generates a slight reverse pressure at the end of the occasional pull (term for pushing water through that came from the old handle machines) that gradually moves the grounds further up with use. It may not be a problem with consumer models - still I prefer not having to deal with it, and 2 years no issues, no service calls, tells me that there might be some truth (half even) to the story.