When I cracked open the box, I saw that the input terminals on the contactor were very corroded, and a strong smell of burnt insulation.
While there was no visible moisture in the box, my guess is condensation, but given my experience with mains electronics, I figured I'd ask if there was anything else I might want to check?
No problem, that looks like heat. I would recommend replacing the contractor and stripping back the wire a little until it is clean and shiny. I would also recommend installing the latest firmware 3.11.3 that includes temperature monitoring and throttling if you have the Color display.
Sounds more like overheating. A less than perfect connection between the input or J1772 wires and the contactor can cause excessive heating of the wires.
Can you post a picture?