ignis akl 335/01 (854133515020) oven still tripping RCD!

I have an split cooker – oven at the top and a grill at the bottom ie two separate compartments. It has 3 control settings – 1) a square with line at the bottom – which we never use, 2) a square with 1 line at top and 1 at bottom – which we always use 3) a square with a wavy line – grill which we never use.

As soon as we set to number 2 setting the house electrics tripped. I changed the rear fan element (accessible from the inside of oven) a few days ago, it now works for half an hour before tripping electrics again (on number 2 setting). I’d thought I’d try number 1 setting (hidden element?), again it worked for half an hour before tripping. This happens regardless what temperature it is set at. The temperature control works ok, light switches on and off. Both fans also work. The replacement element was not genuine, I’ve ordered a genuine one to see whether it makes a difference.

I took the back covers off trying to see if I can find where this hidden lower element fits. I can only see the spade contacts for the fan element and the grill element. I don’t know whether to remove the underlying parts at the back that contain convector fan motor and insulation etc. Is this lower element accessible from the front/side?

I have no manual/service manual. I’m bewildered, I’m not sure what the cause is. If the lower element needs changing I don’t know how to access it. I would be grateful for any advice please. Thank you…kids getting fed up eating at grandmas!!