Ive got a Robur E that sees on average 1.5 shots / day. Ive had it for about a 1.5 years. - I go thru maybe 1/2 lb of coffee per week. About a month ago I noticed it was making a louder vibration noise than usual. It lasted about a week and the louder noise subsided. The normal sound lasted about a week and then it stopped and went back to noisy.

this has happened 3 times now and it is currently quiet today. The grind is not affected as far as I can tell. I have removed the top burr, funnel, tightened everything that could move on it, removed the hopper, cleaned the bottom burr, made sure everything is tight in the burr carrier, etc. There doesnt seem to be anything I can do to make the noise start or stop.

If the grinder is in the "noisy" mode, I can manually run the motor for quite some time, numerous times, but nothing seems to be able to change the noise other than chance. Does anyone have any idea what could be causing this? I have called La Marzocco's Mazzer department, I have called Espresso Parts, Prima Coffee, a local espresso tech and numerous shop owners I know- all with no success in pinpointing the problem or having any insight on possible causes. Has anyone experienced this?

YUP! exactly this! i was just searching for someone who had a similar problem! did you ever get it sorted out?

Can you post a video? Some grinders can 'chirp' a wee bit if there's a stray bit of bean lodged somewhere