Import abort with exception - Duplicate entry '************' for key 'idx_client

Hello

we bought the tool because we want to automate our processes in the future.

Currently we have about 3.000 articles/services/menus in our database. With this tool we want to maintain tens of thousands of articles (journalistic content) and products (thousands of products, trainings and services) in a few days.

We get the following error message when we try to import or update the menus.

Import abort with exception
Duplicate entry '************' for key 'idx_client_id_parent_id_alias_language'

We looked at the *.csv files. The issues confuse us a bit. Here we need help because we have activated the update function in the export.

Import of articles and categories works great.

Ideas?