Steps to reproduce:

1. Use active check, set settings ServerActive in /etc/zabbix/zabbix_agentd.conf

ServerActive=zabbix.standalone.com,zabbix-a.cluster1.com;zabbix-b.cluster1.com

and restart agent

1. Go to web-frontend in zabbix.standalone.com, view Latest data - data is present
2. Go to web-frontend in zabbix-a.cluster1.com or zabbix-b.cluster1.com, view Latest data - data not present
3. Change the sequence of specifying servers in the ServerActive configuration:

ServerActive=zabbix-a.cluster1.com;zabbix-b.cluster1.com,zabbix.standalone.com

and restart agent

1. Go to web-frontend in zabbix.standalone.com, view Latest data - data is present
2. Go to web-frontend in zabbix-a.cluster1.com or zabbix-b.cluster1.com, view Latest data - data is present

Result:

Expected:
I expect that the sequence in which servers are specified should not affect the sending of data.