When working with groups of roofs Dormers do not work properly. See the image below.
The first group (in the blue square) is where the dormer was created. The second group the dormer tears itself apart.
This bug existed in Revit 2017 and still exists to this day. Please consider fixing it.

It would also be very usefull to allow the Join/Unjoin Roof function when working in groups.
