pt-table-checksum says there is a difference but pt-table-sync with --print says nothing

I am using pt-table-checksum to ensure master-slave is synchronized.

When I run pt-table-checksum, I see some differences on employee_profile.trigger_log but when I use pt-table-sync with --print, I see nothing.

I resolved some differences on some tables with pt-table-sync but when I re-test with pt-table-checksum, this tool still says there is a difference.

So what is the problem with pt-table-checksum ? Is is accuracy ?