I've just had a look at mine and trief to clean it out as much as possible with an old tooth brush and hot water. It' now a bit cleaner but still some stubborn marks (in a hard water area of thats of any info).
Would vinegar or bicarb of soda help?
Also, the actual bit of the machine it slots into is just as bad........went with that with a knife and torch! Then vacuumed it up inside.
My machine is a few years old but not that old, feel like I've neglected it badly!
TIA