The GIVI brake light is a touchy piece of work, but when it's all sorted, works very well.
Some of the "sorting" I have had to do has included:
1. Trimming off the pre-tinned ends of the wires because they are brittle, and will leave you scratching your head as to why the contacts stop working after a while. This resulted in the broken off ends (inside the contact housings) getting caught up and holding against the spring-loaded contacts, making one pole of the contact sit higher than the other.
2. Re-soldering one of the light bulb contacts because it came poorly soldered. A little heat and it re-flowed nicely.
3. Putting an o-ring under the contact that comes through the bottom of the rack so that it sits up and makes good contact with the box, rather than settle down into the recess lazily.
4. Figuring out the orientation of the contact housings inside the box such that they all fit properly. It's not particularly obvious at first.
Basically, the ends of the wires are twisted and tinned, to facilitate routing through grommets and such, but this leaves the ends succeptible to breakage later, because they must move a little every time the contacts are pressed together by the closing of the lid or the mounting of the box. This was nice of them to do, but in practice, not so much help.
Shane