Capistrano deploy, sporadic duplicate cronjob entries

Hello,

I am maintaining an application using whenever and, sometimes during deploy with capistrano, I end up with a crontab with duplicates entries, is this a known issue ? I found nothing on the tracker.

Here are the capistrano logs about update_crontab:

02:13 whenever:update_crontab
      01 /usr/local/rvm/bin/rvm 2.2.2@app do bundle exec whenever --update-crontab app --set environment=production --roles=worker
      01 *** schedule.rb, cron loaded
      01 [write] crontab file updated
    ✔ 01 app@xxx 1.295s

Start with the reported Capistrano update_crontab command and its [write] crontab file updated log output. Reproduce repeated deploys with the shown whenever --update-crontab app options and inspect how the crontab is updated; done means identifying and preventing the conditions that create duplicate entries.