Mixing down with default settings reduces the volume

[John Green]

1. Create a new project.
2. Add an audio file.
3. Select File > Mixdown and then export to an ogg file.
3. Select 'Add an audio file' and import the file just saved.

Expected result:
The waveforms should be virtually identical.

Actual result:
See screenshot. In the mixed down version the volume levels are much reduced (looks like about half). I checked in the mix view that the sliders all said 100%. Also note (look at the playhead) that the wave peaks start to get out of line. This is a manifestation of bug #88335. Although they look out of sync playback sounds perfectly in sync.