Creation of pipe and duct systems is extremely difficult with a lot of bugs in the software. I cannot create a duct connection following steps, but reversing or rearranging the same steps it is connect. I have a lot of miracles when creating duct and piping. Revit solution to most sloped sewer pipe connections is the eccentric transition, which does not exist. Need to create flexible couplers "Band-Aid" to properly model sloping sewer pipe!!!!!!