error setting owner of /var/log/weblate/weblate.log.1.gz

We've been getting these daily in the sysadmins list:

From: root@lizard.tails.boum.org (Cron Daemon)
To: root@translate.lizard
Date: Tue, 15 Dec 2020 06:25:16 +0000

/etc/cron.daily/logrotate:
error: destination /var/log/weblate/weblate.log.1.gz already exists, renaming to /var/log/weblate/weblate.log.1.gz-2020121506.backup
error: error setting owner of /var/log/weblate/weblate.log.1.gz to uid 999 and gid 998: Operation not permitted
run-parts: /etc/cron.daily/logrotate exited with return code 1