Did you install certbot via your operating system’s package manager? If so, the package probably provided its own cron job in addition to the one you (I guess) created yourself. That’s likely what you’re seeing in the log.
Yes!
And trying here the cron installed by apt on /etc/cron.d/certbot:
# /etc/cron.d/certbot: crontab entries for the certbot package
#
# Upstream recommends attempting renewal twice a day
#
# Eventually, this will be an opportunity to validate certificates
# haven't been revoked, etc. Renewal will only occur if expiration
# is within 30 days.
SHELL=/bin/sh
PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin
0 */12 * * * root test -x /usr/bin/certbot && perl -e 'sleep int(rand(3600))' && certbot -q renew
Now the question is: is it safe to remove the above cron scheduling, considering I use a custom renew action?