During our extensive testing of the 146 Professional (XP12), we have discovered that certain X-Plane settings can cause issues with how the localiser is displayed on the HSI and flown by the autopilot. 

If the "Disable downwind ILSes" option is enabled in X-Plane settings, the aircraft may have a tendency to fly a reciprocal course (180-degrees out) on any localiser that has a course between 180 and 359 degrees. 

To prevent this behaviour from occurring, please follow these steps:

1.  Launch X-Plane 12

2.  Select "New Flight"

3.  Open the Settings Configuration menu (three sliders icon at top right of page)

4.  In the FLIGHT MODEL section, ensure the "Disable downwind ILSes" box is unticked (or "Disable non-approach ILS's" in later X-Plane 12 builds). 

5.  Select "Done"