It turned out there were several other Orbx airfields similarly affected. Some were just fine. Broome (YBRM) had terrible elevation problems plus misplaced parking. Norfolk Island (YSNF), although not an Orbx airfield, didn't exist from the air, but further down it was in a large hole. Anyway, to cut a frustrating story short, tonight I updated my FSAerodata and Navigraph AIRACS, and low and behold, all my scenery is now back to normal.
Thanks Nick for your input.
Bruce R