ToyLander Electric issues

[Too Late]

Hi all
I have myself a toylander which the kids use. It has 2 car batteries powering 2 motors.

It has recently been blowing bulbs like they are going out of fashion.
I have checked the cabling and its comes straight from the batteries to a chocblock then to the headlights and side lights.

After about 10 mins of use, the lights flicker and go out.

Not good when the sidelights from toylander cost around £30 (inc postage) to replace.
Have tried both 12 and 24v headlight bulbds (side lights bulbs for real cars)

Any ideas where to check?
Otherwise it might be a job to re-wire the lot

Thanks
Nick

[Spare tyre]

Pics needed