Has anybody got a solution for this? It has been a several years now. Why does it still occur? I know there is a work-around by editing the type parameters to show negative values however this is extremely tedious. Whenever i edit the original mass surface, (eg. shift an edge) the sloped glazing/curtain system flips it's orientation. There seems to be now logic or consistency in the way it does this... I this a bug? (if so why has it taken so long for autodesk to fix). Or is the a particular way to edit the mass surfaces without flipping the attached sloped glazing/curtain system?
Try this: turn the reversed panel into a door, reverse the door swing, and then turn it back into the original type of panel. This has worked for me.
There are several alternatives of solutions.