Ugh, this is annoying. Was able to modify the workaround previously mentioned with my wife and I:
Walked away from the vendor/area (north by northeast) Enough for the the NPC to disappear/out of Exodar. Logged off. Logged on. Walked back to the vendor. Once I got it to work, I told my wife exactly what to do and we got it on hers first try.
My theory is that is isn’t necessary what angle it is coming from but from what may be loaded in memory when you interact with the vendor. Coming from the North may be avoiding loading another NPC or something else that is preventing it from working correctly. This is why I was logging off though I don’t think it would be required. I have also considered completely closing the client in position as a troubleshooting step.