Well, what do you know. Minutes after posting my last post, I picked my headphones up and the thing began to come apart in my hands. Thankfully, I was expecting it after some of the posts I read here and was able to ensure there was no loss of screws, washers or the spring.
Because it came apart all on its own I was able to get the headphone back on and retained. There's no need to do anything warranty damaging like dismantling the headphone cup. In fact, there is absolutely no need to have access to the screw head at all. You can't turn the screw anyway because of the way it is locked into the headband. Pictures speak a thousand words, so I've attached a few to make things clearer to people.
All I need to do now is get some Loctite 243 to keep the nut secure and retain the cap properly. That thing is kept on purely using the adhesion of thread-lock cement and not very much of it either.
From what I can ascertain, this problem is entirely to do with the assembly line and inadequate application of the thread cement. It beggars belief that such a small thing could cause so many headaches.
Here's all the components that fell off in the order that I found them.
From left to right: The bolt. The washer. The spring. Two Washers. The Nut. The Cap. And finally, the tiny, tiny piece of old locking cement.
This is the hollow where you need to place the spring, the two washers and the nut. The cap then goes on top.
The oval washer needs to go on top of here between the gimbal and the headband.
Fully reassembled. The nut was tightened up using the tweezers from a mini swiss-army knife. Nothing else I had was small or precise enough for the job. That little knife comes in useful every single day.
