Make sure you've updated to the latest version. There have been a lot of threads lately where people were running version 13.5.1 and thought they were on the latest, but that's not the latest! There have been many significant playback issues fixed in the updates leading up to 13.7.1 on Windows and 13.7.2 on Mac.
Also, make sure you read up on previewing in CC 2015. Things are very different compared to other versions. See this blog post the AE team put out when CC 2015 first launched: all about previews in After Effects CC 2015 (13.5) And this page covers some of the big improvements made in updates since then: Preview without rendering in After Effects
If after all that it continues to not work well for you, it is very easy to install CC 2014 alongside CC 2015. How to Find and Install Previous Version of Adobe Apps in CC 2015
AE CC 2014 can open projects created with AE CC 2015 without issue. In fact, I do this all the time. I usually work in CC 2015 because the interface and workflow is a lot snappier and then I render with CC 2014 to utilize multiprocessing. You may have noticed that feature missing from CC 2015. There are a few other things missing: features not available in After Effects CC 2015
I don't blame you for wanting to go back. AE CC 2015 is the first step in a major re-architecture, separating the renderer from the UI for the first time in AE's 20+ year history. This is a big job and it's clearly still in progress. It's a necessary step for improving After Effects performance, but it's taking a while (and multiple versions) for them to get through it. So, during this time of transition as they're introducing elements of the new architecture, sometimes it may be easier to use the older version to get a job done.
Again, I'd suggest making sure you're running 13.7.1 or later version of After Effects first as a lot of the kinds of issues you refer to have been fixed, but if all else fails, you can use CC 2014 and wait for the next update to AE (which Adobe just released a bunch of sneak peek videos about).
If you are running 13.7.1 or greater and want to file a bug report, here's the link: Feature Request/Bug Report Form
Thank you for the reply, I'm running 18.104.22.168
Yeah the previews/ram preview is all over the place when I'm animating.
It just decides to jump around and not consistent, I've been seeing issue with it on both the macbook pro a our new mac pros.
I can understand some of the new preview features but I don't think it's very useful at this point.
Also the previews are showing glitches on effects sure as CC radial fast blur at 100% and some other effect glitches.
Well, according to the sneak peek videos, there's going to be a brand new preview playback system, so hopefully those bugs will be gone in the next update that comes out.
In the meantime, enjoy the calm, warm comfort of the old RAM preview in CC 2014!
lol man, I will take care, and thank you for your help.