The z/OS (MVS) Event Monitor crashes following an IPL of the LPAR and the crash appears to happen also because the Event Monitor tries to load a Filter File that does not exist.
The filter file is created as part of the Event but if for some reason the filter is NOT created, e.g due to missing privileges on the Mainframe, the Event does not create any warnings or errors.
Bug in Event Monitor 12.3.x
Release : 12.3
Component : AUTOMATION ENGINE
Sub-Component: Agent MVS
Verify the existence of the Filter File prior to launching the Event.
Update the Agent z/OS (Event Monitor) to version 12.3.5 or superior where the issue does no longer occur.