Update: I've identified the trigger of this condition on our network as PI's "Wireless Configuration Audit" background task which executes on 3850 stacks. All "Error, ECI has run out of event blocks" syslog events over months happened while that task...
Update:
See CSCuw53025. Workaround: monitor syslog for "Error, ECI has run out of event blocks" and pull affected systems out of NMSs likely to run "show run". This buys time for a remote reload.
This popped up on two 03.06.03E 3850 switch stacks recently. The "show run" command causes hung sessions. PI apparently polls configs often.
Apparently when the VTYs become exhausted, EEM scripts fail.
2015-10-08T20:01:18.306 10.10.10.10 <187>29620: ...