Its the youtek technology making the racquet go stiff at the last point of impact. The stiffness then transferring the shock to your arm. You're also using stiffer poly's. Which is shrinking the sweet spot. Try using a soft poly or hybrid-ing with a multifillament.
I used to own one of these and I swapped it with a friend because when I added lead to it, it would go way to stiff to quickly.. especially on the back scratch part of my serve...
I personally think this is why head has stopped using Youtek and Innegra and moved forward to the graphene compositions.
Yes, we know it's all about the technique. But if your racquet collapses every time you volley..you need to add some lead to it...