Table mysql/innodb_index_stats has length mismatch in the column name table_name. Please run mysql_upgrade

In mysqld.log I have thousands of lines like:

Table mysql/innodb_index_stats has length mismatch in the column name table_name.  Please run mysql_upgrade

So, according to virtually every post on the matter (and error msg itself):

mysql_upgrade -u root -p

Enter password: 
Checking if update is needed.
Checking server version.
Running queries to upgrade MySQL server.
Checking system database.
...

and all tables in all databases are like

...
mysql.columns_priv                                 OK
mysql.db                                           OK
mysql.engine_cost                                  OK
mysql.event                                        OK
mysql.func                                         OK
mysql.general_log                                  OK
mysql.gtid_executed                                OK
mysql.help_category                                OK
mysql.help_keyword                                 OK
mysql.help_relation                                OK
mysql.help_topic                                   OK
mysql.innodb_index_stats                           OK
mysql.innodb_table_stats                           OK
mysql.ndb_binlog_index                             OK
mysql.plugin                                       OK
mysql.proc                                         OK
mysql.procs_priv                                   OK
mysql.proxies_priv                                 OK
mysql.server_cost                                  OK
mysql.servers                                      OK
mysql.slave_master_info                            OK
mysql.slave_relay_log_info                         OK
mysql.slave_worker_info                            OK
mysql.slow_log                                     OK
mysql.tables_priv                                  OK
mysql.time_zone                                    OK
mysql.time_zone_leap_second                        OK
mysql.time_zone_name                               OK
mysql.time_zone_transition                         OK
mysql.time_zone_transition_type                    OK
mysql.user                                         OK
The sys schema is already up to date (version 1.5.1).
Checking databases.
...

But, I am still getting the error in the log

2019-01-27T18:37:15.304587Z 66190 [Warning] InnoDB: Table mysql/innodb_table_stats has length mismatch in the column name table_name.  Please run mysql_upgrade
2019-01-27T18:37:15.304620Z 66190 [Warning] InnoDB: Table mysql/innodb_index_stats has length mismatch in the column name table_name.  Please run mysql_upgrade
2019-01-27T18:37:15.304684Z 66190 [Warning] InnoDB: Table mysql/innodb_table_stats has length mismatch in the column name table_name.  Please run mysql_upgrade
2019-01-27T18:37:15.304707Z 66190 [Warning] InnoDB: Table mysql/innodb_index_stats has length mismatch in the column name table_name.  Please run mysql_upgrade

The structure appears to be okay. Is there a config issue? Please advise.

The answer appears to be – reboot server. I do not have rights to do this, but after admin rebooted, issue appears to be resolved. Not sure why just rebooting MySQL did not fix?