Cyberdemon, ralphzoontjens thank you for the advice. Much appreciated your time and input.
The area is designed to be smooth and most of the case after the injection, it remains smooth. However, in some failed test injections there were some few chairs that had a small bump there.
The manufacturer has done the slicing but it’s very difficult to observe flow/direction of the glass-fiber as it is used the 1mm length one. From what engineers saw, they could not notice something strange. All seemed usual they said.
The mold flow analysis did show the stress is focused on the gate area. But the white mark didn’t happen on all the products. Some are just fine.
Here are some more pics of the injection gate area and some other failed chairs.
Thanks again!