zabbix server 3.4.11 often restart itself and log "too many open files"

[roses]

Hi all,
After upgraded zabbix server from 3.2.1 to 3.4.11, I found that zabbix might crash and then restart itself, and I found these in zabbix_server.log:

zabbix_server [25699]: failed to open log file: [24] Too many open files
zabbix_server [25699]: failed to write [cannot accept incoming IPC connection: [24] Too many open files] into log file

But I believe that the number of file descriptor is enough:
# ulimit -n
65535

Dose anybody have the same situation like me ? How do you solved this problem?

[kloczek]

But I believe that the number of file descriptor is enough:
# ulimit -n
65535

Above it is ulimit of the root user. Zabbix processes are usually running under zabbix user/group.