ORA-16686: database may not receive redo data if redo source is an alternate destination

DGMGRL> show configuration;

Configuration - dg_prd1203

  Protection Mode: MaxPerformance

  Members:

  p1203s1  - Primary database

    p1203fs2 - Far sync instance

      prd1203  - Physical standby database

      p1203s2  - Physical standby database

        Warning: ORA-16686: database may not receive redo data if redo source is an alternate destination

  Members Not Receiving Redo:

  p1203fs  - Far sync instance (disabled)

Fast-Start Failover: DISABLED

Configuration Status:

WARNING   (status updated 48 seconds ago)

Current situation, the redo source for p1203s2 is FAR_SYNC p1203fs2 that is not alternate destination of primary p1203s1. The alternate destination of p1203s1 is prd1203.

How to resolve the problem? I cannot add second ALT by using "edit database ...." command. I try the following command but failed.