This error occurs when the key field in the datasource app being copied has duplicate values, which violates Kintone’s restrictions.
If you encounter this error, you may need to adjust the settings of the Kintone form and, in some cases, modify the individual records. Please visit this page for guidance on how to change the form settings.
If you cannot set the field to prevent duplicates (for instance, when looking up employee names), you’ll need to change the field that acts as the lookup key.
Please watch the video “Do You Have a Key in Your Record? ~Kintone Basics~” to understand the concept of “key” and work on it. This video is available only in Japanese.