I've got the same problem, and nobody seem to help. All i can find is bullcrap talk about the audio scrub bug.
This is another ongoing issue with AE CC and Yosemite, I'm afraid there is no answer you are going to like! Adobe should never have said AE was Yosemite ready as it clearly isn't. Just another example of the ever decreasing customer faith in Adobe, and their ability to address major issues in a timely manner.
Current major bugs:
Loss of import requiring restart.
2 or more frames RAM preview error.
Skipping the first few frames of any RAM preview.
Not releasing RAM after quitting AE.
No good Adobe pointing people to articles they have written saying some of these things don't work! Just bloody fix them and stop releasing such buggy software!!!
Very sorry you have hit this bug. We do know about the issue and are working on a fix. We apologize for the inconvenience.