Had the rear loosen up a few times. Took it apart, cleaned it up really well with alcohol and blue lock-tighted the lock nuts on. You can't over tighten them because the axle bottoms out inside the freehub body. Did this about 3 weeks ago and have ridden about 10 times, haven't had any problems since. Also, keep you thru axle clean and greased.
I think I'm going to have to change the free hub bearings in mine, started getting play in the cassette and its not the lock ring..... Also I'm sure I can't get it to go as quickly as I used to
I have tools to take apart this hub, PM or email me direct for more info, logofreak@shaw.ca http://forums.mtbr.com/specialized/hi-lo-rear-disc-hub-service-replacement-869150.html
I had issues with the Wheelset that came on my 2013 Stumpjumper Comp Evo. There was play in both hubs. Specialized support recommended putting green locktite in and around the end caps of both hubs, which lessened the issue but it wasn't a fix by any means. Specialized ended up giving me a store credit for the value of the wheelset. Never had any issues with the Roval hubs on the aftermarket wheels though, those have been extremely solid.
If there are any old school riders out there looking to rebuild their Hi Lo Rear Hub, I ,ade a very detailed video about how to do it. Take a look. https://youtu.be/6qPJIkepQEM