I've assigned security permissions so anonymous users can use the Poll SCM now feature for all jobs, but not Build Now. If I restart Jenkins though, it says there is Old Data that needs to be removed, and recommends me to use the Manage Old Data feature to get rid of it. Specifically:
IllegalArgumentException: Failed to parse 'hudson.model.Item.Poll:anonymous' — no such permission
If I go into Global Security Configuration, and enable Poll and click save, the issue goes away until next restart.