Hello Kuan Yi Wu,
Is the Shipper screen customized? If so, have you tried the same operation in Standard Mode?
Also, it would be helpful to run a trace in SQL Profiler. Please see instructions and use the template that you will flind in KnowledgeBase article 967955. See what area has a long duration. It would be best to do this when there are not a lot of users in the system.
Let me know what you find.