Elasticsearch snapshot stuck for several days

We are having issues with a snapshot that failed to complete or timeout. It's been running now for 7 days.

"snapshots": [
"snapshot": "curator-20160528130005",
"version_id": 1070199,
"version": "1.7.1",
"indices": [
"state": "IN_PROGRESS",
"start_time": "2016-05-28T13:00:10.565Z",
"start_time_in_millis": 1464440410565,
"failures": [],
"shards": {
"total": 0,
"failed": 0,
"successful": 0

We are also unable to delete the snapshot, the command hangs.

curl -XDELETE "localhost:9200/_snapshot/es_snapshots/curator-20160528130005"

Is there any way to force this? We have put off rolling restarts of cluster nodes due to the size of the cluster and recovery times.

Many thanks,

Full Cluster restart fixed the issue