Cant stop/start mysql

I have an issue after upgrade mysql percona xtradbcluster version 57.

i try to re upgrade percona xtradb cluster with remove dir.
i do this :
1.stop mysql and remove curent config
2.remove percona >> apt-get remove --purge percona-xtrabackup* percona-xtradb-cluster* (remove dir ? oke)

export LC_ALL=C
3.install pxc 57 >> apt-get install percona-xtradb-cluster-57
4.stop mysql >> /etc/init.d/mysql stop the node with your previous configuration (join to other node)
6.start mysql >> /etc/init.d/mysql start . in this step , i got failed to start. but when i ps -ax |grep mysql, mysql can login
7.mysql_upgrade > Open another session and run >>> mysql_upgrade -uroot -pkaskus

  1. start mysql >> /etc/init.d/mysql start [failed] but when i ps -ax |grep mysql, its available and can login when i stop >> /etc/init.d/mysql stop , it cant be

mysql is run and upgrade, but stop/start mysql not going well.
can you help me???
i got this issue and i cant fix
please help