I installed the leads for a battery tender onto my car's battery terminals. The terminal clamp bolts/nuts were VERY difficult to unscrew for attaching the leads.
I believed that they were cinched tight and then the threads were peened or some loctite was used. Regardless, they were so difficult to remove, it felt cross-threaded.
On reassembly, one went one - still a little tough. But the other had damaged threads. I replaced the bolt & nut with a similar sized unit from a local auto parts store - but ti wasn't a battery terminal bolt, as the Cayman uses a smaller bolt.
I wanted to replace those with the original factory ones (color me a purist). Anyway, they can't be ordered. They aren't in the parts book. You have to buy an entire friggin cable!! (I'm not that much of a purist).
As it turns out, batteries in newer Porsches usually start failing in about two years, according to the Porsche parts dept. At that time, they will have a first hand look at what I discovered.