Symptoms in zabbix agent log:

Failed to execute command "/etc/zabbix/scripts/exim-ping.sh": Timeout while executing a shell script.
Failed to execute command "/etc/zabbix/scripts/phpfpm.sh php7-www ": Timeout while executing a shell script.

Solution:

echo "Timeout=30" >> /etc/zabbix/zabbix_agentd.conf