Hi Lorraine, when I have encountered problems very similar to what you describe it has always come down to wrong configuration of the ODBC drivers. It is very important that the codepage that is specified is correct.
Do you know which IBM codepage they are using in the location in China when they update the database? What does the IBM iSeries/DB2 database say itself about the database and tables where the data is located? When it comes to codepage?
Codepage is particular character set being used. They are numbered and are made for catering for different countries, languages and scripts. In IBM lingo they are identified by a Coded Character Set Identifier (CCSID).
It is not so important what the iSeries computer use but rather what the DB2-database you are accessing is using. Here is IBM's recipe to find it: https://www.ibm.com/support/knowledgecenter/en/SSEPEK_11.0.0/char/src/tpc/db2z_determineccsiddb2data.html
If you want a more in-depth explanation then you could read this: https://www.ibm.com/developerworks/data/library/techarticle/dm-0506chong/index.html
The trick is to determine the DB2 EBCDIC codepage and set the same codepage in the ODBC-driver (or iSeries/DB-driver that you have on the Qlik Sense server or desktop).