Adobe After Effects cc 2017 - Audio slows down and then speeds up at random

I've got this figured out on my system after no luck with any of the suggestions in this thread including the so called previous SOLVED solution with no luck there either. The problem is the Audio Sample Rate in Project Settings under the File menu. The default is 48.000 khz which is too high for real time playback and rarely needed for most projects anyway. Change this to 44.100 which is still a very high quality and that fixed it for me instantly. Also keep in mind that if you move your mouse while playing back, that can also cause the audio to slow down, so change your sample rate and get your hands off your mouse after pressing play and you should be good for perfect playback as long as you first buffered the section of your timeline you want to hear in realtime. The problem is not your hardware, and contrary to what some believe, After Effects is 100% meant for realtime playback for any length of timeline that your system is able to buffer. If you can buffer it, it should play in realtime with no lag. The max buffer time is dependent on your hardware and available cache space. Hope this helps.  

I may have found the solution. I was rendering a cached comp (so playback in real-time) and audio kept sounding slowed down. It's an 48Khz 24bit stereo track in a 48Khz project. The problem was the comps framerate of 29,97 drop frame. When I switched it to 25fps, the track sounds perfect. When I switch back and fourth between framerates, I can toggle the problem on and off 🙂 

--> I think AE has a bug where it samples the audio files incorrectly with certain combinations of frame rates and audio sampling frequencies.

I'm finding this issue with CC2019. My system is a Core i7 Xeon 20 core CPU, 128gb RAM and a 24gb Nvidia card. My colleague and I putting together clips in AE for use in PP. I'm finding that when I do a RAM preview, even with just an HD 1920 clip playing with speech audio - ie no effects that have to be rendered on the fly - it still slows to a crawl and the audio sounds worse than Sylvester Stallone after 14 pints of beer. 

Now if AE was processing a ton of effects at once, even with 128GB, I would understand the slow down, but this is just an mp4 slotted in over a voice over playing at 1/4

So is it because I'm doing things wrong with compositions? The more layers in compositions, the quicker it ram previews?

thanks

Gutter-Fish is telling you right. Same thing happened to me and I had to drop my Preview res down to 1/4 until I got things better organized. Like I had multiple clips in my project without any In/Out points set. Once I got those points set, I could increase my Preview res back up to 50%

Does this help?

Preferences > Previews > Mute audio when preview is not realtime