The error you've encountered indicates the timeout of the upstream container. It means that the request to the server is taking too long to process, causing the timeout. One possible cause is due to large file uploads. It is also possible that Cloud Run might not have enough memory and CPU for file processing which is why it works well locally. You might need to configure it and set memory limits.

As mentioned by Chris, it might be helpful to change the default timeout value. Aside from that, you can implement logging and tracing so you'll be able to know exactly what process is taking too much time. You can read this documentation about logging and viewing logs in Cloud Run.