Sunbeam — sunbeam 5.5 litre crockpot

I have had my Sunbeam Crockpot for about 4 years. It is in immaculate condition and is used maybe once a fortnight, mainly in winter. Today I put a rolled leg of lamb in it and cooked it for about 6 hours. When I was washing it up tonight, I discovered a dirty patch in the stainless steel base. I went looking in the crock and discovered a crack down the side. It has not been knocked or dropped. I am very disappointed that this has happened as I have never had a problem with Sunbeam kitchen appliances. I would really like my crockpot to be replaced as I do not think it can be mended.
The crack is between the silver lines in the photograph.
Kind regards,
Dianne Hitzke