500 error. No suitable servers found (`serverSelectionTryOnce` set)

Plz help! Sometimes (often) get 500 error. I am using kubernetes + mongodb (replicaSet).
Cockpit version 0.11.2
Mongo version 4.2.6
my config.php
‘database’ => [
‘server’ => ‘mongodb://mongo.mongo.svc.cluster.local:27017/cockpitdb?replicaSet=rs0’
]