Basically, (only on Beta) it loses the (meta)data in Redis, then the browser tests start failing because it can't show suggestions.
This is easily worked around by re-populating Redis, but it shouldn't be happening to begin with
Command to re-populate Redis:
foreachwikiindblist gettingstarted-with-category-suggestions.dblist extensions/GettingStarted/maintenance/populate_categories.php
This has happened at least twice now.