title_body: Coffee machine repair
upvoted_answer: I'd start by contacting their customer support for a service manual and for tips on this particular problem.
  
  The key idea in debugging (diagnosing) is to think of hypotheses that could explain it, and ways to test those hypotheses, then do the tests.
  
  E.g. for this symptom, my first hypothesis is that there's a switch or optical sensor or other sensor to protect the mechanism, and the sensor could be clogged or covered with gunk.
  
  It's good to think of multiple hypotheses and tests to distinguish between them. So here's another: The mechanism itself could be clogged with gunk, and after detecting too much load or force, the control software backs off for protection.
  
  A test for both of these hypotheses is to open the machine and clean the works. The difference between the two hypotheses is whether it's the sensor or the mechanism that needs cleaning.
  
  The service manual would help with hypothesis generation and testing. What start up checks does it do? What &amp; where are the sensors? What parts need to work properly for the grinder engagement mechanism to work?
  
  Another hypothesis: The mechanism needs lubrication. The service manual should indicate what to lubricate, what not to lubricate, and what lube to use. Or you could guess.
  
  Another hypothesis is a rubber O-ring has worn out or broken. This is also consistent with what you've written, i.e. your existing experience can rule out some hypotheses. It can also make other hypotheses less likely, e.g. if the cause is the same as last time (not a sure bet), a burned out motor would've cost you for parts, while a worn out O-ring might not have.
  
  Also: There are local and online repair clinics to help with appliance repair.
  
  It's worth trying. In the worst case, you spend some time and learn something.