Hi there, I am literally in the middle of dealing witht he erxact same problem. I've used Saniflo producxts for aboiut 12 years and have always known them to typically have a life span of about 2 - 3 years (certainly not the 13 they claim!) but as there is nothing else like it on the market I've learned to sucki it and see... I'm guessing the problem sounds like the macerator should be running but isn't... hence the "grinding noise"
Typically the things that tend to go wron in my experience is that someone forgets about not putting anything else more solid than a poo or paper in the toilet, or not keeping the system cleaned out with a monthly descale.
If I find anything else I'll let you now - try speaking to Saniflo they're fairly helpful and have a reputation to try to look after...
Merry Xmas
Mark Sn13 0HY, December 2009