After issuing 'cpstop;cpstart' commands on the Standby VSX cluster member, the output of 'cphaprob -a if' command shows the following state of the Sync interface configured on Bond interface:

• The state of Sync interface as 'UP' in the context of VSX itself (VS0).

• The state of Sync interface as 'DOWN' for each Virtual System.

  Show / Hide example
  
  

  vsid 0:
  ------
  Required interfaces: 3
  Required secured interfaces: 1
  
  wrp1       UP                    non sync(non secured), multicast
  bond2      UP                    non sync(non secured), multicast, bond High Availability
  bond4      UP                    sync(secured), broadcast, bond High Availability 
  
  vsid 2:
  ------
  Required interfaces: 3
  Required secured interfaces: 1
  
  bond4      DOWN            sync(secured), broadcast, bond High Availability
  wrp129     UP                    non sync(non secured), multicast
  wrp128     UP                    non sync(non secured), multicast
   
  vsid 7:
  ------
  Required interfaces: 4
  Required secured interfaces: 1
  
  bond4      DOWN            sync(secured), broadcast, bond High Availability
  wrp448     UP                    non sync(non secured), multicast
  wrp449     UP                    non sync(non secured), multicast
  wrp450     UP                    non sync(non secured), multicast 
  

Reboot of Standby VSX cluster member resolves the issue.