Search head keeps failing in search head cluster

[zzhao05]

This was the search head that kept failing:

splunk > /appl/splunk/bin/splunk show shcluster-status -auth admin:adminpassword

Encountered some errors while trying to obtain sh cluster status.
This node is not the captain of the search head cluster, and we could not determine the current captain. The cluster is either in the process of electing a new captain, or this member hasn't joined the pool

splunk > /appl/splunk/bin/splunk show shcluster-status -auth admin:Adm\!n4Splk

On the other hand, the other 2 SHs look ok when I issued shcluster-status command on CLI:
Captain:

    dynamic_captain : 1
                               elected_captain : Tue Jun  4 12:47:03 2019
                                            id : A6F265E7-5FEC-448A-9ACD-8FE901D045D5
                              initialized_flag : 0
                                         label : pgv013d27
                                      mgmt_uri : https://172.26.42.160:8089
                         min_peers_joined_flag : 0
                          rolling_restart_flag : 0
                            service_ready_flag : 0

 Members: 
        pgv013aba
                                         label : pgv013aba
                         last_conf_replication : Tue Jun  4 14:04:23 2019
                                      mgmt_uri : https://172.26.96.216:8089
                                mgmt_uri_alias : https://172.26.96.216:8089
                                        status : Up
        pgv013d27
                                         label : pgv013d27
                                      mgmt_uri : https://172.26.42.160:8089
                                mgmt_uri_alias : https://172.26.42.160:8089
                                        status : Up

I did check with the forum and made sure that the mgmt_url was correct in server.conf..

It worked for a while but it started failing again after a while.
And I see the captain was selected and up and running. not sure why on the failing SH, it shows cannot determine the current captain.. Any advise where else shall I check?
Thanks.

[codebuilder]

Within server.conf, make sure that the pass4SymmKey is set correctly under both the [general] and [shclustering] stanzas on the failing node, then cycle splunk and re-evaluate.