Moodle 2.0.10 Backup and Restore Problem: Partial Data only during migration

Dear all,

I am currently using Moodle version 2.0.10 and I am planning to move host using backup and restore function. Every time I backup my courses, it looks like it succeed (no error or warning given). However, when I try to restore the backup file, all participants are migrated successfully, but only partial grade migrated (for example, out of 500 users only 50 grade data migrated).

I tried to restore in Moodle 2.6 and the same 2.0 environment with no avail. 

Any help on this will be much appreciated. 

Thank you in advance.