GI circuits are fairly well known to overheat due to excessive bulb current, usually toasting the connectors much like this. If it's been fine up until now, my suspicions would fall on a bulb socket that developed a short, coupled with a GI fuse that is rated too high.
I would double-check all fuse ratings, test for bulb socket shorting, rebuild that crispy connector (and probably replace that relay, which looks fried), and give serious consideration to converting your GI to LEDs.