Black (rust colour) stains in the carafe
The fact that is is a stainless steel container makes it highly unlikely that it is rust. You should never drink out of a rust container. I would suggest a highly caustic but non-toxic cleaning agent. I'd start with vinegar or lemon juice. If you can get your hand in there, let it sit for a while and give it a scrub. Steel wool would definitely get the nasty stuff off but may also compromise any type of protective coating so inspect the metal to see if it has any type of coating over it (like an enamel glaze) should be bare stainless though.
I've had my pepper mill less than a month, have
Sporadic operation indicates an intermittent (flaky) connection. Check the tightness of the battery terminals as well as checking for corrosion. If it can be made to work by fiddling with the button, then the button may be failing.
Not finding what you are looking for?