Prefade send creates phantom audio

Mixing dialogue I have track sending to a reverb bus. Bizarrely the effect bus plays it's audio about two seconds ahead of the dry signal, which plays properly, not delayed. Even more bizzarrely sometimes the problem would go away in playback, but would re-emerge when exporting the project.

I rebooted, restarted and made sure I was updated to the latest Audition version. I even tried changing buffer size. I conducted many tests to isolate the problem.

Eventually I was able to determine that it was a prefade send creating the phantom pre-play. When switching the effects bus to post fade the problem disappeared from both playback and export.

This is fine as I was able to make adjustments to the effects with the send post fade, but I am perplexed by the problem and might really want to use a prefade send one day. What could explain this behavior?