Hotpoint eg76x grill

Question

The grill in my oven has developed a fault - to begin with it didn't work when the k**b was turned to the highest setting on full grill, but now it is very hit and miss what will work. The fan sometimes works for the grill, sometimes not. I can get the grill itself to come on but not in all positions on the k**b where it should. Is this a problem with the k**b or the grill? Thank you.