Thank you for your offer. I am located in Malaysia (Probably I am at the other end of the globe).
You are right, i googled in the web for meaning of 'galling' and found the exact description to my current problem. There are some 'pimples' or 'asperity' on the the mold, which I believed resulting from rubbing of 2 steels.
The mold construction was quite complicated: 2 slides from the side. And the galling happened the mating surface of these 2 sliders. The steel hardness is 340-370 HB. ( http://assab-hk.com/ASPAC_718_Hi_Hard_EN.pdf
). Based on the tool drawing, I believed that both sliders and core cavity side is made from same steel.
The mold was made locally in Malaysia. (Not China mold).
Indeed we have sent the mold for repairs and move to another molder.
At the moment, it all about who is going to bear the cost.
Thank you once again. I really appreciate you guys help.