To add, this is just an extra issue in China as the customer does not want to register for FX payments and then maybe an audit will follow.
Product will still flow from Korea to China customer anyway. So they send the money to the China plant and then you exchange it into Korean dollars and send it to the Korea plant. The only issue is how the local government might consider this transaction, so spek to an experienced Accountant first.
Regards
Waza