Kibana restarting in a loop


After an upgrade , kibana is restarting in a loop.
On kibana.logs, I can see:

"message":"[{\"type\":\"unavailable_shards_exception\",\"reason\":\"[.kibana_security_solution_8.9.2_001][0] Not enough active copies to meet shard count of [ALL] (have 1, needed 2). Timeout: [1m], request: [BulkShardRequest [[.kibana_security_solution_8.9.2_001][0]] containing [9] requests]\"},

There is other shards in error.

For testing purpose (because its a test environment), I tried to delete the index but showing that it is empty:

elastic@***:~$ curl -X DELETE http://localhost:9200/.kibana_security_solution_8.9.2_001 -H 'Content-Type: application/json' -u elastic --insecure
Enter host password for user 'elastic':
curl: (52) Empty reply from server

Result is that kibana is always on "not ready yet".

Is someone experienced the same issue and able to workaround it ?

Thank you