ZBX-6294 fixed but a similar problem happened again in 4.0
Nodata function behavior is not correspond with documentation: https://www.zabbix.com/documentation/4.0/manual/maintenance
When “no data” maintenance ends, triggers using nodata() function will not fire before the next check during the period they are checking.
If using Default "Template App Zabbix Server" with “no data” maintenance 10 min.
I confirmed all fire "Zabbix agent on Zabbix server is unreachable for 5 minutes" trigger. (agent.ping and nodata(5m)=1)
Look screenshots for getting more information.