Steps to reproduce:

1. Create trigger with multiple generation mode.
2. Create action with multiple steps for the created trigger.
3. Multiple events are created by same trigger.

Result:
All steps are executed with every events.

Expected:
The first step is execute with every events.
Unexecuted steps after that will be executing only on the last event.

It's described in the following document.
https://www.zabbix.com/documentation/5.0/manual/config/notifications/action/escalations
> The execution of each new escalation supersedes the previous escalation, but for at least one escalation step that is always executed on the previous escalation. This behavior is relevant in actions upon events that are created with EVERY problem evaluation of the trigger.

3.0.28 works as expected.