Mostly a bunch of bug fixes have come in the latest two versions of Netty - not sure there is anything specific to TinkerPop that is currently known as a problem, but it's probably good to keep up with these patch releases:
http://netty.io/news/2016/08/29/4-0-41-Final-4-1-5-Final.html
http://netty.io/news/2016/10/14/4-0-42-Final-4-1-6-Final.html
- links to