The Chassis Down alarm is the root cause alarm for the Device Lost Contact alarm in Spectrum. This causes the Device Lost Contact alarm to be hidden by default in the OneClick Alarms tab.
Release: 20.2.x and above
Releases starting from Spectrum 9.2 SP1 bring in additional logic for the ChassisManager which overrules the "Device not responding to polls" / ContactLost_Red Alarm. This logic raises a Chassis Alarm in case the device has an Entity_MIB and makes the ContactLostRed alarm a symptom under the Chassis Alarm.
Check for devices without true chassis/modular build and set the attribute "EnableEntityModuleModeling" to "No". Perform a "Reconfigure Model".
This will switch off the ChassisManager logic for these devices.