Suggests heater fault, may be heater itself, very common, this is an Indesit after all 😥 , could be related wiring or control module.
The only way to be certain is to test the heater etc, with the proper electrical test equipment. If you don’t have access to this try the link in my sig to see if we have someone who can help you.
Plug out at all times if you intend to open the patient up yourself.