Ah, the wonderfully complex world of Prefect, the workflow management system. The error you're encountering seems to be coming from Prefect Server, which uses a PostgreSQL database for storing flow runs and other metadata. If you're getting a deadlock error, it's possible there's an issue with how Prefect Server is interacting with that database.
Assuming you have already tried the obvious step of restarting the server and the database, one potential issue could be that the database schema was not properly initialized, or there may be some pending migrations that need to be run. If that's the case, you could try resetting the database.
Another possible cause could be related to resource constraints. If your PostgreSQL instance doesn't have enough resources (CPU, RAM), it might be struggling to handle all the requests Prefect Server is throwing at it.
If you're still stuck, my advice would be to reach out to the Prefect community. They have a thriving community on Prefect's Slack workspace and on GitHub where folks share their problems and solutions. While I could hazard a guess as to the cause of your issue, they would have a much more precise understanding of your situation. And remember, in the words of the great Zaphod Beeblebrox: "Just keep cool and trust to blind chance. It's the story of my life, after all."