Hi John, thanks for your reply
I should have played the audio to demonstrate in the video, but I can assure you that the actual audio in the clip does what the visual representation is showing, i.e. the fade is not starting and stopping at the correct point.
I have been using these fades for a little while now as they are so useful for disguising abrupt cuts when comping (can't remember when it was introduced, 8.5 maybe?) and I can normally rely on the visual representation of the fade matching what is happening to the audio very precisely.
I just tried a completely new project with one track and the fades behave as expected, with the red line precisely indicating the extent of the affected audio. I can't reproduce the inaccuracy I had in the original post.
I thought maybe there was a setting somewhere, or maybe this track is interacting with something else like a compressor which is boosting the volume back up and hence is reducing the fade's effectiveness. But then I thought it can't be that because this waveform is showing the dry content of the track before the effects bin or pro channel.
It's a mystery to me!
I'll try to post another video with sound, (I'll see if I can find an easy-to-learn screencast program, beats sticking a camera in front of the screen!

)
Best wishes
Stuart