This is a known issue on Mac OS 10.10. It does not affect any version of After Effects on Mac OS 10.9 or earlier. See here:
The problem only occurs on the first playback and does not occur when the playback loops. We are investigating this issue with Apple.
Thanks for the quick response, Tim!
good to know it only happens on the first playback, however I would imagine that this is the "most used" playback (as in, when I'm animating to sound / voice over / etc, I usually stop, adjust as needed, and then re-preview again).
Glad to know the issue is known / being worked on.
Thanks Tim, I was looking if someone else has this problem, there it is.
Just following the thread for fixes, please keep us updated here in the discussion.
Any updates on this? It's really killing me