Plugins were updated, which forces changes to jobs that use plugins that include their version information. Was looking at a job that had a recent change as shown by the job config history plugin. The changes were all plugin version changes, and a specific user, not 'anonymous', was listed. He shouldn't have access rights to update plugins. I asked him if he did, he had no idea what I was talking about.
Looking at the list of similar issues, this might be a duplicate of