Since the upgrade to Zabbix 5.0, we notice that a certain trigger is randomly alerting for 30 seconds.

The expression for this trigger is:

{Template OS Windows Servers:eventlog[System,,Warning,,^(4227)$,1,skip].regexp(^TCP/IP failed to establish an outgoing connection)}=1 and {Template OS Windows Servers:eventlog[System,,Warning,,^(4227)$,1,skip].nodata(8h)}=0

eventlog[System,,Warning,,^(4227)$,1,skip] is an item of type Log that is polled every 5 minutes.

In this screenshot you see that this has happened 7 times today for a specific server:

But if we look at the latest data, the last time this event occurred was 2 weeks ago:

We clearly see that these events started to happen after we upgraded to Zabbix 5.0.1.