The SpectroSERVER was consuming 100% CPU when trying to do a VNA discovery and the devices were not being discovered.
Release : 10.4.1
Component : Spectrum Core / SpectroSERVER
A range discovery with the range of 10.0.0.0 - 10.255.255.255 constitutes a device count of 256*256*256 i.e. trying to discover 16.7M devices was causing the issue.
The 10.0.0.0 - 10.255.255.255 range discovery was causing performance issues on the SpectroSERVER. Deleting the range discovery resolved the performance issue.
A clue that Spectrum is configured for huge discovery ranges is hundreds\thousands of False Management Agent Lost alarms where those devices are responding to SNMP request when polled manually.