Hi
According to my experience you can never add gooseneck vent nozzle without causing some sort of problem! Sometimes you notice the problem immediately sometimes you will notice problem when you want to edit the equipment in the future!
I dealt so many kind of errors and I tried various solutions to solve each one but they were never flawless.
I think Autodesk should totally revise "Vent Nozzle" module on P3D software.