This article explains an issue where management access to the primary node is lost in case of the cluster.

You will not be able to connect to the primary node via SSH or Jweb while as secondary node will be accessible.

This can happen when you configure backup router knob on the cluster for each node but miss to configure a normal static route, as it will help you to access the secondary node but in order to access the primary node you will have to configure a normal static route for the management access from indirect subnets. Please note the backup router configuration is not a replacement for the basic static route.