Constant Netty IllegalReferenceCountException in server

On the latest 15w38a snapshot's server jar, the server continuously throws "io.netty.util.IllegalReferenceCountException: refCnt: 0" errors, apparently when sending chunks to players, as seen in the attached latest-server.log.

Players see lots of missing chunks in the world, and frequently get disconnected. The client logs are full of netty-related "java.util.concurrent.ExecutionException: java.lang.IndexOutOfBoundsException" errors, as seen in the attached latest-client.log