Phantom jobs in sidekiq-cron
Still not entirely sure of the underlying logic. But it appears that sidekiq-cron does not purge jobs which are not found from the scheduled set. It's therefore required to do one of the following before a deploy to remove either all jobs or a specific one:
#destroys all jobs
Sidekiq::Cron::Job.destroy_all!
#destroy job by its name
Sidekiq::Cron::Job.destroy "Job Name"