After the Spectrum upgrade from 10.4.1 to 10.4.2 we recognize SNMP V3 polling issues.
Release : 10.4
Component : Spectrum Core / SpectroSERVER
Please install the patch 10.04.02.01.D87 and add below .vnmrc settings.
delete_unknown_report_type_profiles=FALSE
delete_invalid_profiles=FALSE
delete_invalid_empty_profiles=FALSE
Then request to increase the poll threads to 600 and monitor how it goes.