3727559 - Error encountered while changing synchronization mode: Failed submitting design changes - SAP SRS

• Attempting to change the synchronization mode of HADR using the following command :
        sap_update_replication synchronization_mode, <ACTIVE_SITE_NAME>, async
• Execution failed with error message:
        UpdateReplication  Task Name                     Update Replication
        UpdateReplication  Task State                    Error
        UpdateReplication  Short Description             Update configuration for a currently replicating site.
        UpdateReplication  Long Description              Submitting the design changes for local host 'site1' for server on host 'primary_host_name'.
        UpdateReplication  Failing Command Error Message Failed submitting the design changes for local host 'site1' for server on host 'primary_host_name'. '5' errors.
        UpdateReplication  Additional Info               Submission errors: 'Submitted Entity is not Valid, Unable to connect to host standby_host_name:4909,
• The HADR state remains in an incomplete Distribution Mode after the failure.
• The command sap_status path is reporting the following information: 

 PATH               NAME                      VALUE                    INFO
 ------------------ ------------------------- ------------------------ -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
../..
                    Start Time                2026-02-19 15:38:14.022  Time command started executing.
                    Elapsed Time              00:00:04                 Command execution time.
 Site2              Hostname                  <STANDBY host name>      Logical host name.
 Site2              HADR Status               Standby : Inactive       Identify the primary and standby sites.
 Site2              Synchronization Mode      Synchronous              The configured Synchronization Mode value.
 Site2              Synchronization State     Inactive                 Synchronization Mode in which replication is currently operating.
 Site2              Distribution Mode         Remote                   Configured value for the distribution_mode replication model property.
 Site2              Replication Server Status Active                   The status of Replication Server.
 Site1              Hostname                  <PRIMARY host name>      Logical host name.
 Site1              HADR Status               Primary : Active         Identify the primary and standby sites.
 Site1              Synchronization Mode      Synchronous              The configured Synchronization Mode value.
 Site1              Synchronization State     Asynchronous             Replication Synchronization Mode is currently operating as 'Asynchronous' instead of the configured value 'Synchronous'.  Please refer to Replication Server logs for more details.
 Site1              Distribution Mode         Remote                   Configured value for the distribution_mode replication model property.
 Site1              Replication Server Status Active                   The status of Replication Server.

• SAP Replication Server (SRS) 16.0
• SAP Adaptive Server Enterprise (ASE) 16.0 with Always-on Option (HADR)
• SAP Adaptive Server Enterprise (ASE) 16.0 with High Availability Disaster Recovery (HADR) for Business Suite
• SAP Replication Server (SRS) 16.1
• SAP Adaptive Server Enterprise (ASE) 16.1 with Always-on Option (HADR)
• SAP Adaptive Server Enterprise (ASE) 16.1 with High Availability Disaster Recovery (HADR) for Business Suite

hadr, synchronization mode, async mode, sap_update_replication synchronization_mode, synchronization mode change, Failed submitting the design changes, UpdateReplication, Submission errors, Submitted Entity is not Valid, Unable to connect to host , KBA , BC-SYB-REP-SAP , Replication with SAP Suite / SAP BW , Problem