Transport-level error when refreshing Excel Power Queries

From what you’ve described:

• Errors are intermittent — some users/reports fail while others work.
• Behavior differs if queries are loaded to worksheet vs. connection only.
• This points less to SQL Server itself, and more to how Excel’s Power Query engine is managing connections.

Power Query creates multiple connections in parallel when refreshing, especially when you use “Connection Only” queries feeding into dependent queries.
Some environments (firewalls, load balancers, SQL TCP keepalives, VPNs, or Excel’s own engine limits) can cause those connections to get dropped.

What you can do…

Force Power Query to serialize refreshes

By default, Excel may refresh multiple queries in parallel. To stop race conditions:

• In Excel:
  Data → Get Data → Query Options → Data Load → Background Data → Disable "Allow data preview to download in the background"
• Also:
  Data → Connections → Properties → Enable "Refresh this connection on its own" and disable background refresh.

This forces Excel to keep connections more stable.

Additional…

Avoid unnecessary “Connection Only” dependencies

Check SQL Server settings (Check Timeout)

Check Excel client stability (Ensure all users are on the same build of Excel)

My answers are voluntary and without guarantee!

Hope this will help you.

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