There is a very loud rattling/ vibrating noise coming from the top of the oven beneath the hob. I have carefully unscrewed and lifted the lid of the hob and have identified the source is some sort of small jagged edged roller about the size of a small can of cola. It’s powered by electric and as soon has it starts rolling the noise is deafening. It looks to complicated a job for me so I want to call in the pros but can anyone tell me what this mechanism is called and what is it’s purpose?