1. I bulk added new hosts.
2. Problems have been generated and shown in the problem list.
3. Despite having two notification methods setup (email and telegram) that should get triggered (and worked before... have not been changed.) the action list in the problem overview stayed empty for over an hour.
4. Without changing anything restarting zabbix-server instantly triggered the processing of actions and sent out the notifications (without changing any settings).

Unfortunately i have no clue how to reproduce the case as of now.
System in use is rhel 7.2 and zabbix 3.2.3.