A real "nasty niff" then ?
My old machine got "slimed up" twice (washer blocked)
And some nasty smell and lil black spots.
I put it down to mixing of screenwash additives + I also used to use clearalex powder
After I stuck with using Carplan additive, solely, it never came back. I never use garage water either or pure tap water.
The tap water bit is probably because I have to use Brita filters normally anyway cos of the lime in the water..
I wonder could it be something like,the container shouldnt be airtight and the little pinhole or whatever vent is in the cap is blocked?.
Im only using 10% summer and 20% winter in the Carplan stuff.
Once again maybe not much help^
,but hey Somebody has to win the lottery eventually.