Neff U1721 keeps tripping power circuit?

Neff U1721 double oven started to trip main consumer unit and lower oven element stopped working, but fan and light ok.

Have replaced element which now heats up, but still trips CU after about 30 seconds.

Top oven/grill works ok still along with clock etc. without tripping. Lower oven light works ok until temperature knob turned on. All visible wiring looks ok including to rear of oven and to switch panel. I think I can just see some connections along the left hand side panel but haven't accessed them without removing side panel and I can't see clearly for insulation, although there may be some scorching.

The question is what connections are down the side and is removing the side reasonably easy. I don't want to take the thing to bits if there's nothing down there.

Are there any sites with tech literature or photos of opened up units, exploded view drawings etc? Any ideas or help most welcome.