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 ? [UPDATE] I use pt-table-checksum -h -u -p '' --recursion-method dsn=h=,P=3306,u=,p=,D=check_db,t=dsns --nocheck-binlog-format --set-vars innodb_lock_wait_timeout=50 > ~/stats_check_db_.txt After that, I run command to filter: cat ~/stats_check_db_.txt | awk '{print "*"$3"*" " -- " $8}' | grep -Fv "*0*" This is output: *DIFFS* -- TABLE *1* -- mysql.user *1* -- employee_profile.entry *1* -- employee_profile.ip *1* -- employee_profile.thread When I run pt-table-sync: pt-table-sync --print h=,P=3306,u=,p= --sync-to-master --databases employee_profile --tables entry I see nothing. After a while, when I re-check with pt-table-checksum, I don't see difference on employee_profile.entry For a resolved table, I still see some differences on next re-check. These are disappeared from result of pt-table-checksum on the third checksum. [UPDATE 2] I am using percona toolkit version 2.2.13 - lastest version on http://www.percona.com/ I reviewed all implementations of db server that I did checksum. These are old implementation of mysql or mariadb that someone built them. I see the problem just appear when the implementation between master and slave is different such as master is MariaDB 5.5.34 and slave is MariaDB 5.5.37 (I see false positive error: Cannot nibble table because MySQL chose no index instead of the PRIMARY index - just ignore it and then execute pt-table-sync) or master is mysql 5.5.35 and slave is mysql 5.5.37 (I see pt-table-checksum says there is a difference but pt-table-sync --print says nothing - just re-test for sure). I think it is a reason for false positive errors. Thank you so much !