Do you run #FreeBSD 15? The #syslog_ng project needs your help! We could not reproduce in-house, but there might be a bug in syslog-ng 4.9.0 related to #inotify on FreeBSD 15. Could you test it in your environment?
https://www.syslog-ng.com/community/b/blog/posts/installing-syslog-ng-4-9-0-on-freebsd