The Patch Test starts the full bench (incl. workers) and then runs migrate.
Migrate enqueues orphan-link cleanup jobs (delete_dynamic_links) that the
workers pick up and process while migrate is altering tables, which
intermittently fails with MySQL 1412 'Table definition has changed, please
retry transaction'.
Start every bench process except the workers during migrate, so nothing
consumes the queue mid-migrate. Redis and the other services stay up; the
queued jobs just wait.