Had an instance once on my my old Altea where the headlights were on when ignition was on and the lights were turned off. Dampness. It fixed itself and never came back. The garage did mutter about the lighting control unit being difficult to diagnose, diagnostic charge etc... but since it cleared itself left it after a few days cancelled the appojntment, never came back again.
Once the whole car went dead, had power but wouldnt even turn over. Dampness again. It cleared itself.
Agree it needs proper diagnosis but with any luck it may dry out.