All shards failed exception during reindexing kibana index

Hi,
I am running ELK 7.0.1 cluster in kubernetes environment.
I had few visualizations stored in .kibana_1 index. I have taken the snapshot of this.
Later, .kibana_1 index was deleted & it got recreated when kibana was restarted. The new .kibana has some other saved objects(dashboards, index patterns) etc.

I restored from the snapshot & renamed the restored index as .kibana_1-restored. Now, I have .kibana alias pointing to two .kibana indices.

green open .kibana_1
green open .kibana_1-restored_1565373769

Because I can't load kibana UI when .kibana alias points to two indices, I tried merging the documents from both these indices into one & deleting the other. For merging, I use Re-index API as shown:

curl -HContent-Type:application/json -XPOST "http://$ELASTICSEARCH_SERVICE:$CLIENT_PORT/_reindex?pretty" -d'{
"source": {
"index": "'$source_index'"
},
"dest": {
"index": "'$dest_index'"
}
}'>

With this, I see following error logs in elasticsearch:

{"type":"log","host":"shiv-es-elasticsearch-client-699d5f4fd4-hm58q","level":"WARN","systemid":"a6aab87097d14ff5b192d56f1d73ff1a","time": "2019-08-09T13:57:01.055Z","logger":"o.e.i.r.TransportReindexAction","timezone":"UTC","marker":"[shiv-es-elasticsearch-client-699d5f4fd4-hm58q] ","log":"giving up on search because it failed with a non-retryable exception"}
org.elasticsearch.action.search.SearchPhaseExecutionException: all shards failed
at org.elasticsearch.action.search.AbstractSearchAsyncAction.onPhaseFailure(AbstractSearchAsyncAction.java:296) ~[elasticsearch-7.0.1.jar:7.0.1]
at org.elasticsearch.action.search.AbstractSearchAsyncAction.executeNextPhase(AbstractSearchAsyncAction.java:139) ~[elasticsearch-7.0.1.jar:7.0.1]
at org.elasticsearch.action.search.AbstractSearchAsyncAction.onPhaseDone(AbstractSearchAsyncAction.java:259) ~[elasticsearch-7.0.1.jar:7.0.1]
at org.elasticsearch.action.search.InitialSearchPhase.onShardFailure(InitialSearchPhase.java:105) ~[elasticsearch-7.0.1.jar:7.0.1]
at org.elasticsearch.action.search.InitialSearchPhase.lambda$performPhaseOnShard$1(InitialSearchPhase.java:251) ~[elasticsearch-7.0.1.jar:7.0.1]
at org.elasticsearch.action.search.InitialSearchPhase$1.doRun(InitialSearchPhase.java:172) [elasticsearch-7.0.1.jar:7.0.1]
at org.elasticsearch.common.util.concurrent.AbstractRunnable.run(AbstractRunnable.java:37) [elasticsearch-7.0.1.jar:7.0.1]
at org.elasticsearch.common.util.concurrent.TimedRunnable.doRun(TimedRunnable.java:41) [elasticsearch-7.0.1.jar:7.0.1]
at org.elasticsearch.common.util.concurrent.ThreadContext$ContextPreservingAbstractRunnable.doRun(ThreadContext.java:751) [elasticsearch-7.0.1.jar:7.0.1]
at org.elasticsearch.common.util.concurrent.AbstractRunnable.run(AbstractRunnable.java:37) [elasticsearch-7.0.1.jar:7.0.1]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:11

The indices did not get reindexed as the documents from .kibana_1-restored did not get copied to .kibana_1. In this case, to access kibana, I will have to delete either of these kibana indices but this will result in loss of saved objects (on the UI).
Can you tell me if the approach to re-index kibana indices using re-index api is correct? If yes, what could be causing this error here?

Thanks,
Shivani