It appears that utf-8 characters are stored differently by frontend and server with DB2 databases.

For example if item value contains utf-8 character string then server handles it normally (stores in database, sends in alert messages etc), but frontend strips all utf-8 characters from this value.

When trying to view utf-8 character data written in database by frontend (for example in host inventory) it has different format than the data written by server.

This might be some configuration issue, so needs to be investigated first.