Hotpoint BU72 Double Oven/grill. 18 months since purchase, but only about 10 months of use The lower oven has stopped working about 5 minutes after switching on.It tripped the rcd. The top oven and grill still work and the fan still goes. I have removed the panel and looked at the fan element without removing it but cannot see or feel any damage.Do these elements fail without any visible sign of damage or is it likely to be something else? We are fairly isolated here and service calls are expensive…. Thanks.