OK, so we've set a Project North, and set a base point for our Shared Coordinates so that when we export a plan to AutoCAD it always is located and orientated correctly. Works great.

However, if we export the sheet that the plan is on, and Revit sets it up with the whole AIA x-refing scheme, the base x-ref Revit creates isn't in the right place or orientated correctly relative to our Shared Coordinate system. It's like it 'forgets' if we export from the sheet.

Looks like it's just a bug in Revit 8.1, but wanted to throw it out there for everyone to watch out for...