Nextcloud 11 - syslog flooding

I have Nextcloud 11 configured to use syslog. It seems to work fine until I go to the admin page and click ‘logging’. Then syslog floods with error messages at least 5-6 per second.

Feb 28 14:25:50 Nextcloud[2000]: {PHP} fseek() expects parameter 1 to be resource, boolean given at /var/www/nextcloud/apps/logreader/log/logiterator.php#81

Linux Debian 8.7, x64
MariaDB 10