Cannot dispose of CodecIndexOutput: Object reference not set to an instance of an object

Seeing the following errors in our RavenDB for Octopus and our performance seems to be impacted.

System.NullReferenceException: Object reference not set to an instance of an object.
at Raven.Database.Indexing.LuceneCodecDirectory.CodecIndexOutput.Dispose(Boolean disposing) in c:\Builds\RavenDB-Stable\Raven.Database\Indexing\LuceneCodecDirectory.cs:line 189
at Raven.Database.Indexing.LuceneCodecDirectory.CodecIndexOutput.Finalize() in c:\Builds\RavenDB-Stable\Raven.Database\Indexing\LuceneCodecDirectory.cs:line 171