PID installation in Gaggia Classic causing shortcircuits

Hi guys, I’ve installed a Rex C100 controller following these instructions: https://heald.ca/adding-a-diy-pid-to-the-gaggia-classic-pro/

this guide is for the “new classic” , but I think the mains power is coming from the same switch in my machine (lower left hand spade connector) which is an RI9303/03. Please correct me if I am wrong

Connected here, I plugged it into the wall and turned it on and it lasted about 5 seconds; the PID powered on and then a huge bang and flipped the circuit breaker at my house. This spade connector on the front switch is now slightly blackened. I am not sure if this indicates arcing at this position?

Ive attached a whole bunch of images of all of the connections and wiring, please if you could let me know where you think I have gone wrong, I am in over my head a bit with this project. Any help with be greatly appreciated 🙂