Halfway through playing an animation with audio, the audio will skip back a second and then keep playing. This will only happen after the first playthrough of the animation. It always happens around the halfway mark, frame count does not affect this. Audio error does not affect animation. Can be avoided by stopping and then replaying the animation manually.
It happened to me too, even if I manually stop and replay the whole thing again, the audio would randomly jump back to somewhere around the beginning. This bug wastes a lot of time when I want to see if my animation syncs without rendering, since I also had the audio scrubbing bug (does not play correct chunk for the FPS e.g chunk plays for 12 FPS but the whole animation is 6 FPS)
I suspect though that this is a problem with QtMultiMedia which we use for playback. I'm not sure it's actually fixable :-(
*** This bug has been marked as a duplicate of bug 385589 ***