what is the source of odour from our 18 year old Dimplex convector elements?

we have a 18 year old Dimplex CXL24storage/convector heater and there is a pungent, sweet sickly smell associated with the use of the 2 kw convectorelements. I wonder if it is the degradation of perhaps the resin binding the particles of the insulator strip to which the element s are stitched . If so their replacement with new elements should theoretically eliminate the problem. The heat from the storage block side of things seems to be of neutral odour. Has anyone else had this problem with old products of this type?