I am having the exact same issue, did you ever find a solution? The only thing i can think is that when stp is creating the aff and associated files it becomes unresponsive, i thought that it was crashing at first until i realised that it was still populating the destination folder and becomes responsive once it has finished. we are finishing audio for a short film and have to hand off to a mixer who needs aff or omf and we are stuck.
any help or suggestions would be much appreciated.
cheers