Vague replication error code 2005
Once you change the master_host, you have to redo everything else

It says so in the MySQL Documentation on CHANGE MASTER TO


  If you specify the MASTER_HOST or MASTER_PORT option, the slave assumes that the master server is different from before (even if the option value is the same as its current value.) In this case, the old values for the master binary log file name and position are considered no longer applicable, so if you do not specify MASTER_LOG_FILE and MASTER_LOG_POS in the statement, MASTER_LOG_FILE='' and MASTER_LOG_POS=4 are silently appended to it.


Just specify everything again

STOP SLAVE;
CHANGE MASTER TO
    master_host='IP_of_new_host',
    master_port=3306,
    master_user='repluser',
    master_password='repluserpasswowrd',
    master_heartbeat_period=1,
    master_auto_position=1
;
START SLAVE;


GIVE IT A TRY !!!