The ZABBIX server seems to reset the Agent Port value back to the default value of 10050 despite it was being explicitly set to another value (10500).

How to reproduce:

• Configure ZABBIX agent on some remote host(s) to listen to port 10500
• In ZABBIX GUI, use "Mass update" to set the the Agent Port for the reconfigured hosts to 10500
• From now, the servers are reachable again (Server asks Zabbix Agent on Port 10500)
• Wait some time (20-30 Minutes)
• See that the agent port has been reset to the default value of 10050, thus makes the agent unusable

Additional notes:

• Some (2 out of 60) hosts seem to be immune against this
• Environment has been upgraded from 1.6.4 to 1.7.1

How to fix:

• unknown -