Hello!
Are both commands executed from one action and one script?
Please show the action and script configuration.
Also, please show trigger configuration, are both hosts used in the trigger?

Yes both commands are executed in one action, the scripts are different, the writting value to turn ON is different than the writting value to turn OFF.

the script is a SNMPSET string:

snmpset -v2c -c {SNMP.COMMUNITY} {HOST.IP} {SNMP.OID} i {SNMP.WRITTINGVALUE}

The only real macro in the script is *

* the others I altered for the sake of posting this issue.

Trigger expression:

last(/Template HVAC/OnOffAirCon)={SNMP.WRITTINGVALUE}

Both Hosts use the same Template, diferent IP and Name for each host.

The action steps are sellecting the correct script, but the second step even though its configured to send the command to HOST.2, it fills the IP of HOST.1 address in the script.

Script Configuration 

Note: the turn ON script is basicaly the same only difference is the SNMP Value.

Action Configuration

Can you also show the trigger configuration? Is the problem detected on host1 only?

The problem happens for all hosts I've tested, it seems like Zabbix is "saving" the IP from the first step, and populates this IP in every step. Even though another Host is being called as can be seem from the images provided.

I've tested with multiple Hosts and the problem happens everytime with this version of Zabbix.

Trigger configuration is bellow:

And action report, I redacted some information. The IP address only shows the lasted digit. And we can see the instances where the action conditions we're met,  it sends a command to turn ON (49) Host1 then, 1-3 minutes later it sends a command to turn OFF (48) Host2, but the IP is the same.

The problem is not in the action conditions or Steps, because this exact same actions is being used correctly in Zabbix 4.4.

Confirmed
In my scenario there is host "test" with no interface.
In action I try to execute script:

echo {HOST.IP} >> /var/log/zabbix/action.test.log

And use host "host 1" with interface 10.1.1.1:

In the file I get:

 *UNKNOWN*

Which means it's trying to resolve it on host "test", that doesn't have an interface, not on "host 1" which I selected.