You can check this setting within Google Apps:
1. Click the Settings gear icon (⚙) near your Gmail's top right corner.
2. Select Settings from the menu that comes up.
3. Go to the Forwarding and POP/IMAP tab.
4. Change Folder Size Limits to Do not limit the number of messages in an IMAP folder (default).
5. Click Save Changes.
6. Re-run the migration.