Audio keyframes out of sync on export

Hello

I have found for a few years now, that often when exporting a video, the audio ducking is out of sync from where I have keyframed it on the timeline.  For example, the audio levels raise about a second too early before the narrator finishes speaking. I have had this issue again today on a very simple video with no audio effects added.  I have tried exporting it as H264 and ProRes. Also exported it from Premiere, and in Media Encoder with the same outcome.

Any ideas why this may be happening? In the past I have had to export the video to find out where this issues happen, then bring the affected keyframes forward a second, so that it sounds correct in the next exported video.