Is there a problem with the limit condition when putting a non-uniqueness field in the order by clause in the MySQL 5.6 version?

Hello, I'm writing because I have a question about mySQL query. The query is thrown in the form of a bulletin board list, and the query is as follows.

1page

select * from table_name where ~~~~ order by DueDate limit 0,15;

2page

select * from table_name where ~~~~ order by DueDate limit 15,15;

This is a query that shows 15 times for each page, and I am using limit in mysql.

The problem is that the record on page 1 appears again on page 2.(Except for the where and limit conditions, one case is certain.)

I think this phenomenon occurs because the DueDate field applied to order by is not a unique field such as PK or index.

order by DueDate, tableid gave PK to the conditional clause, but it is normal if it is modified like this.

Does this problem occur if a field that does not have uniqueness is placed under the order by condition?