Earth lead corrosion leading to inverter not working

[Shaun Witts]

Just read this thread and realise it’s old and resolved now but might be worth mentioning though that I think LOZ cottoned the elephant in the room is galvanic action. I suspect the vehicle has been used in a salty environment frequently. The aluminium wire has been doing exactly what a sacrificial anode on a boat will do. Gradually lose its mass to the more noble metal, the steel of the chassis. I’ve seen1kilo sacrificial anodes virtually eaten down to their bolts in just two years.

Almost certainly the case, and a good example of that phenomenon.
However, I do not live on the coast, and I don't drive in winter any more than anyone else so my van's exposure to salt is normal for this country.
As @oldiebut goodie said, CCA cable is totally unsuited for vehicle use - especially if exposed to the elements.