New stinky sauna smell is usually not to bad.
Ring the supplier tell them you want a new heating elemant fitted.
They should of offered it in the first place why should you have to clean your purchased heater.
1. you have an awfull smell, which you dont know could be fumes..??
2. you didnt pay for a dirty smelly spoilt heating elemant
3. you dont know what damage long term the stuff on it could do.
4. its not what you paid for.
I know its hard and its another hick up, its fustrating and exhausting.
Its not what you paid for and its disrespectfull for them to expect you to accept it like it.
If you feel strong enough tell them so. xx
sleep on it and see how you feel tomorrow.
Jules x Sorry i get so cross with things like this