Hi
Thanks for all the suggestions.

I switched the lights around yesterday, thinking it could be a faulty
fitting or globe/bulb, still remains the same.

I will do a voltage test on the w/e and see if there is any major
difference between lights 1 through 6.

There are also two connections between lights 2 and 3 that I want to
check, one that joins the two cables and one of course where light 2
joins the cable.

I do not know the gauge of the wire in American standards but it is 1.5
mm single core wire. The lights are wired in parallel as it is an AC
circuit, I believe there is not another option.