Strange Lights and dead powerbox

One of my customers has a physically modified Twizy, and it has a set f LED lights. It also has a powerbox. We have just noticed that when the handbrake is off the rear sidelights glow. At the same time the powerbox is now just showing a Blue screen and no data. Looking in the small usb socket, it was badly corroded, guess its leaking rather than sealing. This may have to be replaced, and they are going to contact powerbox directly about this. But the lights is a strange thing. When handbrake is on there are two contacts that short to earth on the mechanism, so Im guessing this is probably an earthing / back flow of power some way. I dont have a wiring diagram yet, but hoping to get this from a friendly Renault dealer.
All fuses in order and functional.
Any thoughts? .

You can disconnect the powerbox and it should keep the “tune”. I would try that.

I expect the brake lights is an Earth isssue, as you say.

The Twizy doesn’t like allbtypes of Led lights try swapping them back.

The power box is now disconnected. The LEDs have been on it for about two years. Not an issue previously.