Master slave replication duplicate error message 1062 [on hold]

I am facing

Last_Error: Error 'Duplicate entry 'plhvjq1vsbj77hatr0ggnuecn4' for key 'PRIMARY'' on query"

and

Last_SQL_Error: Error 'Duplicate entry 'r36m06fqp4mshqtdtr3n1t4450' for key 'PRIMARY'' on query. Default database: 'mydb'.
Query: 'INSERT INTO `mytable` (`id`, `modification`, `lifting`, `data`) VALUES ('r36m06fqp4mshqtdtr3n1t4450', '1477572991', '31536000," '')'

...after every 2 minutes on all my 4 slaves. I do not know what the problem is. It started yesterday and still continues. How can it happen that these duplicate values pass from master to slaves and stop replication?

The new duplicate entry has the same primary key but different data for remaining column. Table is using MyISAM engine with MySQL version 5.1. Its structure is:

    CREATE TABLE `mytable` (
   `id` char(32) NOT NULL DEFAULT '',
   `modification` int(11) DEFAULT NULL,
   `lifeting int(11) DEFAULT NULL,
   `data` mediumtext,
    PRIMARY KEY (`id`),
    KEY `idx2` (`modification`)
    ) ENGINE=MyISAM DEFAULT CHARSET=latin1