Scag electrical issues

I have a Scag Liberty with a Kohler KT750 motor. The blades stopped during mowing, shutoff engine then would not restart. Found ground wire running from solenoid ground to engine ground melted. I cut the harness open to check wire bundle. The only wire melted was ground. Anybody have any ideas why only ground would be bad?

The only two reasons would be high resistance causing heat and melting the wire, or high amperage from being shorted to battery voltage causing heat and melting the wire.