This issue is now fixed with a beta version of MPC-HC and new LAV filters but the MPC-HC is not released as a stable version yet.
Here's the links you need if you are running MPC-HC/LAV
I just re-installed over the top of the current stable versions and checked Expendables 3 - worked perfectly.
https://trac.mpc-hc.org/ticket/4879 --> if you go to the bottom of this thread there is a link to the "nightly build" where you can d/l a version that works with Atmos discs (it doesn't play the atmos info of course, it just ignores it and plays the 5/7.1 True HD)
https://github.com/Nevcairiel/LAVFilters/releases --> lates 0.63 release here.
Hope this helps all those struggling with Atmos encoded discs
