I wish I had a solution for you. I don't! I can however let you know that you are not alone in this.
I am a long time user and a true FAN of Adobe Products - especially After Effects.... That said, this 2015 AE release is buggy at best.
The RAM Preview (now called Preview) does not work as well as the 2014 version and the Audio now skips at random times. I'm running an i7 with 24 Gig of ram, my video card is a NVidia 960 GX, and the Preview is still terrible.
Usually when there's a major upgrade, you can run your old version in parallel for a while. That wasn't true this time.
I felt a little uneasy when they said they were uninstalling 2014 versions in favor of the 2015 versions, but I'm such a fan, that I figured they'd have this right. I was actually looking forward to the upgrade. What I found instead is a buggy shell of the wonderful 2014 version of AE. I don't think it's possible to roll back - I wish it were.
I certainly hope they get this straightened out.
What exactly gave you the faith that 2015 would be the miracle cure to AE's long and ongoing problems? I really wouldn't take much notice of Adobe's marketing razzamataz! Like watching Hooli's Nucleus launch!
You should know by now that Adobe releases updates to software to arbitrary dates set by CC. Whether the software is ready or not you are getting it!
They and just about anyone else with half a brain did also give out instructions on how to keep 2014. You would literally have to be crazy to trust Adobe and believe any of their claims on new releases.
You can reinstall 2014 in the side tab in CC. Go back to 2014 and the first 1 sec of RAM preview not showing, import files randomly stopping, memory leaks and the infamous collect files don't touch the mouse error! although all these still occur in 2015 too!
AE = Nucleus!
Thank you for letting me know about the reinstall for 2014. It may not be perfect, but it is a lot better than 2015 at this point in time.
Knowing that will help a lot in the near term.
I appreciate your help.
Sorry to anyone seeing this in the future. I deleted the original video. Hopefully this all gets sorted out in an update eventually.
Does not fix any preview issues on my fully loaded 5K Retina iMac, and I'm NOT going to just work on one monitor. Fix your embarrassing mess, Adobe!