"Don't know about your setup, but when I see the vapor on mine (which is all copper 10 gallon)is at the end when I turn up the heat for collecting feints.
If I were to guess without seeing what you have, I would think you may be running a little too hot ! When all is running normal on mine, the output lines below the condenser is cool to just warm to the touch.The vapor you are seeing is running so fast it cannot condense into liquid. If it were me, I would turn down the heat a little or increase the cooling water, both has an effect on vapor you are seeing. Usually when running too fast or too hot, you can smell the oils in your output and when this happens you will also get off flavors as well. If on a stripping run it makes little difference but on a spirit run it will ruin the whole process unless you carbon it, but I'm not a fan of carbon. If everything is done pretty close to right there is no need for carbon."