I just competed a flight in the 767 from KSEA to KSFO.  Started the default flight supplied by Captain Sim, 767 at KSEA runway 34R.  Then changed the flight plan to a previously saved flight to San Francisco.  This is the first flight I have made in the 767 since installing FSX Steam.  Had no problems during the flight - it followed all the heading changes programmed into the FMS.  Made an auto landing at KSFO.  I monitor the VAS, and use Plan-G on a networked computer to aid in situational awareness.  Also use Active Sky 2016 for real-time weather.

So when running FSX-SE the 767 has no problems following the flight plan

Jim Kaye  :) :)