Hi
Just found something similar but not connected with export....

The short sound clip highlighted (56 seconds) has a 1 second fade-in and a 1second fade-out. It has not been speed changed..(There is a known bug regarding sound fades on clips where the speed has been altered...but this may be connected to that.)
When the timeline is played from before this clip (e.g. the displayed cursor line position) it starts and fades-in OK but then fades out after 16 seconds!
If played from a point WITHIN the fade -in, the clip fadeout starts at the same place.
One the clip has faded-out stopping starting from the same place restores the sound and then it plays OK to the end.
This actual clip is a section of a longer track that has been split in several places to produce several shorter clips which also have fade-ins and fades-outs. As outlined in a later post inadvertent splits were made to both tracks due to the second split button covering the Play button. So its a bit of a mess at the moment. Still, this shouldn't happen.
If I just have Fade-in it plays OK
If I just have a Fade-out it plays OK
If there is Fade-in AND a Fade-out it fails to play to the end.
So it seems to be connected with the Fade effect.
Nat