Hi everybody. I'm writing this just to help anyone who is trying export an aaf file using logic pro x.
First I tried davinci resolve since it is free and other people told me that its a good roundtrip fcpx to davinci and then export aaf. From Fcpx to davinci I had many issues like davinci not importing aiff files.
So I tried logic. First of all if you need to send an xml from fcpx to logic without much concern for the video since you are going to use a lowress video file as reference, then you should send xml version 1.5 and audio (not extented).
And from logic to aaf export your timeline should be atleast in two parts if your timeline is 45min or more. I had a 90min timeline and when I exported an aaf as one part protools couldn't import the aaf file. Without changing anything it worked as two parts.