Parts printed in Grey V3 will be mechanically similar to those printed in V2. The Young’s Modulus (correlates with stiffness) is the same across both materials and the biggest difference is the elongation at break which is slightly reduced in Grey V3 meaning that you will get slightly less flexion before break but not to the degree you’re seeing.
It’s important to re-generate support structures previously used for Grey V2 because we did modify the support placement algorithm for the new material. If that doesn’t help, you should open a ticket with our support team so that we can help to troubleshoot.