Cannot edit relationship

Hi Testeri  ,
Thanks for reaching out to the Microsoft fabric community forum.

The PBIX file may have become corrupted, try clearing the cache and restarting Power BI Desktop. Save your work first, then navigate to File -> Options and settings -> Options -> Data Load -> Clear Cache. After clearing the cache, restart Power BI Desktop and attempt the operation again.
If the issue still persists after clearing the cache and restarting, you may need to create a new PBIX file, re-import the same tables, and rebuild the report within the new file to resolve any underlying corruption.

If you find this post helpful, please mark it as an "Accept as Solution" and consider giving a KUDOS. Feel free to reach out if you need further assistance.
Thank you