It was mentioned that plastic does not retain odours, but it has been my experience that they do. Just think of when you leave onions in a tupperware container! Many of today's machines have a lot of plastic, so yes, it could be holding the smell there.
I too was thinking of the case as the problem. I'd remove it from the case and work on the two separately, and in different locations. Give the whole machine a good wipe down and not put it back in the case, til I see how it is.
If the smell is that bad, it could be that the odour is now hanging in the room where you have been keeping it. So better get that air cleared out, or else you might have the machine issue solved, but be thinking it is still a problem, when it is really the residual.
A product I might try for odour removal would be Murphy's Cleaner with Orange Oil. Read the label first, to make sure it is OK for how you will be using it.