Case.
An email was received from a reader indicating a possible duplicate publication of article 1 that appeared in the journal and a similar publication that appeared in another journal a year earlier. The editor immediately wrote to the author and the editor of the other journal expressing his concern. The author responded five days later, saying that he did not believe the papers were duplicates. The articles were sent to the COPE chairman, who believed that article 1 fell within the definition of republication because the database, methods, and conclusions were the same in both articles. In addition, the authors did not refer to their previous article when submitting the article.

COPE advice.
It was suggested that the editor may have wanted to consult with the members of the editorial board first before making any final decision, but it was felt that in the end he had no choice but to retract the article that appeared in his journal. It was also suggested that the editor of the other journal be contacted as there may be copyright issues that need to be addressed, and that the copyright institution be contacted to inform them of the decision.

Source: https://entc.com.ua/uk/1990-dublyuyucha-publikatsiya