Audio sounds fine in the timeline but changes in export

Hi all. So I was editing a video like I do everyday, the video has 2 audio tracks one with dialogue and one with music. The music track is ducked against dialogue and all seems fine in the timeline. However when I export it the music randomly goes up in volume where it shouldnt go. Its not the ducking as it goes up in random points no matter if there is dialogue or not. It has only happened to me twice ever! Any ideas why it only does it in the exported file and not in the timeline? And how do I fix this?