Hi
In Power BI desktop, the connector connect to Google Analytics rely on the Google Analytics Core Reporting API. The API may change in a way that affects the results of the queries we generate. Please refer to this article: Google Analytics connector for Power BI Desktop.
In your scenario, please try to update the desktop to the newest version. Also based on this article, I would suggest you post a thread here to discuss the custom dimension related to google-analytics-api.
Best Regards,
Qiuyun Yu