Elastic Search - Failed to Merge Error

Elastic Search - Failed to Merge Error

We have a cluster of 3 servers with 5 indices each with 5 shards and 1
replica, we have been experiencing some weird error, this is taken from
the logs:
[2013-08-12 15:02:42,156][WARN ][index.merge.scheduler ] [Strongarm]
[index3][3] failed to merge
java.io.FileNotFoundException: _10va_e.del
at
org.elasticsearch.index.store.Store$StoreDirectory.fileLength(Store.java:448)
at org.apache.lucene.index.SegmentInfo.sizeInBytes(SegmentInfo.java:303)
at
org.apache.lucene.index.MergePolicy$OneMerge.totalBytesSize(MergePolicy.java:174)
at
org.apache.lucene.index.TrackingConcurrentMergeScheduler.doMerge(TrackingConcurrentMergeScheduler.java:81)
at
org.apache.lucene.index.ConcurrentMergeScheduler$MergeThread.run(ConcurrentMergeScheduler.java:456)
Once this error happens the affected index cannot receive new documents to
be indexed, we have to restart the server in order for the server to work
again, We are running ElasticSearch 0.19.11, with
Java(TM) SE Runtime Environment (build 1.7.0_21-b11)
Java HotSpot(TM) 64-Bit Server VM (build 23.21-b01, mixed mode)
Can anyone point us in the right direction on how to solve this?
Thanks!