Beam 2.48.0 has a bug in the PubsubIO implementation which limits the size of messages. See this issue, which will be fixed in Beam 2.49.0 and incorporated into our next Scio release.
You can read more about upgrading to Scio 0.13.0 in our Migration Guide, the full Release Notes, or the full changelog. If you have any questions or comments, you can find us in the #scio channel on Slack, or file an issue at spotify/scio