Google Analytics has a Query Explorer which can be used to troubleshoot your Google Analytics data source.
1. Make sure you are logged in to the Google account that has access to the Analytics property and select it.
2. Select these parameters in the form:
start date and end date, choose the date for the period where you see a mismatch (important if you troubleshoot a data source with 9 dimensions, you can only troubleshoot single day intervals)
metrics, choose the metrics where you see the discrepancy
dimensions, (important to choose date and all the dimensions you have in your data source. If you troubleshoot a 9 dimension data source, date must not be included)
To find out which dimensions that are included in your data source, you can see an overview under the definition label in the data source details page in Funnel. If the list is too long to view you can check the "Edit Configuration" window.
3. Final step, scroll down and click "Make request" button. The result can be viewed as a table or as JSON and you can use that result to compare them to your Data Explorer in Funnel. Comparing the values is done row by row to the rows in Funnel data explorer.
Note that metric aggregations might not match between the Query Explorer and Funnel, this is expected, read more on why in our troubleshooting article.