Unable to create new bucket

Hello,

I'm having a strange error with the creation of buckets on a couchbase cluster.

I tryed throught web interface and couchbase-cli with the following command:
couchbase-cli bucket-create -c localhost:8091 -uMyLogin -pMyPassword --bucket=mybucket--bucket-port=11223 --bucket-ramsize=20480 --bucket-type=memcached --bucket-replica=0

But I'm just having an http 500 : unexpected error.
By digging logs I found this:

[
"web request failed",
{path,"/pools/default/buckets/"},
{type,exit},
{what,
{noproc,
{
gen_fsm,sync_send_event,
[
{global,ns_orchestrator},
{
create_bucket,
memcached,
"mybucket",
[{ram_quota,21474836480}, {auth_type,none}, {moxi_port,11223}]
},
infinity
]
}
}
},
{
trace,
[
{gen_fsm,sync_send_event,3},
{menelaus_web_buckets,do_bucket_create,2},
{menelaus_web_buckets,handle_bucket_create,2},
{menelaus_web,loop,3},
{mochiweb_http,headers,5},
{proc_lib,init_p_do_apply,3}
]
}
]

I am looking for a way to fix that without restarting the other memcached buckets started on my cluster.

Thank you for any clue.