A few times i have noticed that after I have performed a wash and
removed the clothes, a few days laster my washing machine has had about
2 inches of water in the drum. Im not sure when exactly this happens
but when i open the door at the front the water smells a bit bad (im
assuming its been there for a day or two, just not noticed), on one
occasion i had clothes in the drum about to be washed and the water had
entered the drum and again it wasnt the nicest smell in the world
If I put the machine onto Drain, the water drains away bit it leaves a
whiteish residue on the drum wall which washes away if i do a Rinse
Any ideas whats causing this?

TIA
Doug