If it's manky, I'd scrub it with bleach and a toothbrush. Wear swimming goggles or similar, as it'll splat. Also wear an old top.
Then, do a super-hot wash, with a load of soda crystals.
I say this as previously I had a washing machine that stunk so bad, that we ended up buying a new one . The old one was old, but worked perfectly well-ish. But the seal was so bad, it would have needed to be replaced... and the old machine was not worth it.
So now, even though I am a complete slattern, I pay heed to my washing machine's cleanliness!