My old fusebox with failing headlights circuit, sidelights come on randomly, no headlights, full beam ok (common issue)
The fusebox

The headlamp relay socket

The laminates that make up the fusebox are damp with signs of oxidation.
This is the outer cover removed, here is the area directly behind the headlamp relay

Rivets drilled out and all laminates separated
More corrosion

Opened out like a book

Fully opened out and separated

There was no physical damage to the metal tracks but 2 were shorting behind the headlamp relay due to the melting, they could be repaired though by insulating if needed.
.
Whether the damp caused high resistance and melted the relay holder is not known but if your headlights have the symptoms described above or similar then this could well be the issue