Getting duplicated primary key entry in mysqldump file

Question

We have a mysql 5.1.73 server and a myisam table (we're migrating to later version of mysql and innodb as part of this eventually).

We do a mysqldump every night of a table.

Basic table structure is like

CREATE TABLE `view` (
  `view_id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `created` datetime NOT NULL,
  `person_id` int(10) unsigned NOT NULL,
...
PRIMARY KEY (`view_id`)
) ENGINE=MyISAM ...

There are over 300 million entries.

When we try and import into a different database we get an error (after its imported already 95% of the table fine).

ERROR 1062 (23000) at line 24941: Duplicate entry '303732287' for key 'PRIMARY'

I've searched on that error, and there's a few potentially misleading reasons. So I thought I would check the file direct first.

On inspection of the file, there is indeed a duplicate

grep -o -P '\(303732287.{0,2000}' stats_view_20231101.sql

(303732287,'2023-03-26 00:54:27',1623240508 ... (then some other unique entries)
(303732287,'2023-03-26 00:54:27',1623240508 ... (then some other unique entries different to above).

(if I grep other id's I only get one entry, so I think the grep is ok)

I'm trying to understand why the dump has duplicate entries for a primary key ?

If I look at the live table with

select * from view where view_id=303732284;

303732287 | 2023-03-26 00:54:27 | 1623240508...
1 row in set (0.00 sec)

So the original has 1 entry, but the mysqldump has 2. Any idea what is happening here (and how to get around it)?

edit: I can restore past the error using mysql -f and there's only 1 error out of 300 million entries, but I'd still like to understand what may have happened.