Zabbix Problems Auto-Resolving?

[NightEdition]

I am trying to understand why some of my problems are auto-resolving in Zabbix v4.

I have one item which captures all Critical (Zabbix severity of disaster, level 9) and Error (Zabbix severity of High, level 4) Events from a Windows Event Log (i.e. DFS Replication).
I then have separate triggers for each event ID that I wish to generate problems for.
My problems do not have recovery expressions.
An example for the item and a trigger for event ID 4004 is shown below:

Template: DFS Replication Events Template
Item Name: DFS Replication: Critical and Error Events
Key: eventlog[DFSReplication,,(Critical|Error),,,,skip]

Trigger Name: DFS Replication Event 4004
Severity: High
Trigger Expression:

{DFS Replication Events Template:eventlog[DFS Replication,,(Critical|Error),,,,skip].logseverity()}=4
and
{DFS Replication Events Template:eventlog[DFS Replication,,(Critical|Error),,,,skip].logeventid(^4004$)}=1

OK Event Generation: Expression
Problem Event Generation Mode: Single
OK Event Closes: All problems

What I find is that event ID 4004 occurs, a problem is generated, and is auto-resolved by Zabbix. The event details state it has been "resolved by: trigger".

Can someone please explain why such problems would auto-resolve?

Thanks.

[cyber]

Your item catches critical and error events.
Your trigger activates if item value contains specific eventID and special severity. error and 4004 in your example...
Now, when your item is picking up another value, expression is recalculated and if it does not match conditions any more, trigger value turns to false, problem is closed... marking it as "resolved by trigger".
As yo have multipe triggers based on the same item, probably some other problem fires at that moment.
Absolutely no magic here..

If you set OK generation to none, they will never resolve. But if you do not set generation mode to multiple, you will only catch first match and no more until you have manually (or by correlation) closed old problem.

[NightEdition]

I'm thinking it might be auto-resolving as I have "OK Event Generation" set to "Expression" rather than "None".
Is this likely the case?

[cyber]

Your item catches critical and error events.
Your trigger activates if item value contains specific eventID and special severity. error and 4004 in your example...
Now, when your item is picking up another value, expression is recalculated and if it does not match conditions any more, trigger value turns to false, problem is closed... marking it as "resolved by trigger".
As yo have multipe triggers based on the same item, probably some other problem fires at that moment.
Absolutely no magic here..

If you set OK generation to none, they will never resolve. But if you do not set generation mode to multiple, you will only catch first match and no more until you have manually (or by correlation) closed old problem.

[NightEdition]

Thanks for clarifying.

This makes sense why I have only experienced this on triggers that are linked to an item that targets multiple event IDs, and not an item which targets an individual event ID.