@Mariusz Czak​ :

Here are a few things you can check:

1. Make sure that you are passing all the required parameters to the Create a dashboard object API endpoint. Check the API documentation to see if there are any parameters that you might have missed.
2. Verify that the widget IDs in the original dashboard are unique and that they are not used in any other dashboards or widgets in the new workspace. If the IDs are not unique, it could cause conflicts during the copying process.
3. Check if the widgets in the original dashboard are using any resources or connections that are not available in the new workspace. If so, you may need to create those resources or connections in the new workspace before you can successfully copy the dashboard.
4. Try creating a new dashboard manually in the new workspace and add a few widgets to it. Then, retrieve the definition of the new dashboard and compare it to the definition of the original dashboard to see if there are any differences. This may give you some clues as to what might be causing the issue.

Let me know if any of the above suggestions work for you, if not we can try and figure out more.