Public API: updating existing contents generates a "SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry (...)" SQL error

If a content in eng-GB is updated using the public API, the following SQL error occurs:

[PDOException]
SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '1544-3' for key 'PRIMARY'

Steps to reproduce:

Please adapt the test command attached and run it:

php ezpublish/console silversolutions:translation --env=dev

It creates content and adds a translation. After this it tries to update the eng-GB object and it leads to the exception.