Steps to reproduce:

1. There were events in 10/2021, e.g.:

There are not events with negative duration.

2. Configuration > Services, linked to MongoDB monitoring triggers:

MongoDB subtree was configured chronologically after events above occured. I was reading https://www.zabbix.com/documentation/current/manual/it_services about details of these calculations (e.g. exactly when they occur), but the detail was not enough for me. Maybe events from triggers referenced from service tree need to occur before service tree configuration? If so, maybe more details could be added to documentation and problem solved ...

3. Trigger dependency is as follows (but I tried also drop all trigger dependencies temporarily, but it haven't any impact on service tree resulted below - I did not simulate events re-occurence after temporary disablement of trigger dependencies):

Result:

In Monitoring > Services, SLA report for last 30 days shows 100% availability:

Expected:
Availability reported below 100% (in case tree calculates from events history - not sure in this point).

I know, there are going to be huge improvements of this functionality in ZBX 6.0, so feel free to close this if this is dead development branch  - just let us know, optimally via documentation referenced above, please . Thank you.

Richard