ST3042 tripping RCD

[paulswanton]

I've just got an ST3042 from ebay (charity donation so can't really go back to them). The machine starts to heat then trips my RCD. I've looked at previous threads which mention potential issues with wires catching the lid. It trips with both the lid open and lid closed, with the top heater and both heaters so it doesn't seem to relate to that. I've also had the lid off and all wires seem to be intact and connected ok. I've noticed the metal coiled tubing around the wires is also earthed / is that normal?

I'm based in Milton Keynes / any ideas of 1. what the issue might be or 2 (most likely) anyone locally who'll be able to take a look at it?

Thanks in advance