I have recently encountered the following errors:
Transfer run failed due to internal errors. Please try again later.
The thing is; we have multiple salesforce tables to be extracted, many have succeed. All of which have the same settings and configurations in the Bigquery data transfer, yet somehow, these particular table(s) have been constantly failing due to internal errors. Unfortuntately, there's no specific error cause in the bigquery data transfer log.
What might be the cause of internal error in Bigquery Data Transfer service?
Or are there any specific permission or anything else required to configure the salesforce's connected app to get the Salesforce data such as User, Payment, AccrualReportItem that might have caused this?
There can be a lot of reasons of internal error with the BigQuery Data Transfer Services -- in which the log should have given you more information.
It could be a time-out, it could be certain columns are null from salesforce, etc. Without the log, there's no way to figure what exactly is wrong with the out.
In my case, the log did not show the error details until certain "X"th processes. You could reach out to the Google Supports if this remains to be the issue.
Regarding the salesforce connected app; you can refer to the manage connected app > under "OAuth Scopes" to review what the client has control over when accessing the SFDC through the connected app.
Assuming you have granted the "full access" there should not be a permission issue in accessing the data that the user have the full-access to. Hence, also make sure what data the user have access to.