Preview is stuck in a loop and is unresponsive

same issue:
iMac (Retina 5K, 27-inch, 2020)
8 GB 2667 MHz DDR4
Macintosh HD
AMD Radeon Pro 5300 4 GB

Same issue:
MacBook Pro 15" Retina Mid-2015, macOS Catalina 10.15.7
2.2 GHz Quad-Core i7
16 GB RAM
Graphics: Intel Iris Pro 1536 MB

AE: 17.5.0 (build 40)

Same issue:
MacBook Pro 15" Retina Mid-2015, macOS Catalina 10.15.7
2.2 GHz Quad-Core i7
16 GB RAM
Graphics: Intel Iris Pro 1536 MB

AE: 17.5.0 (build 40)

Same issue. Especially on short sequence lengths I can't get it to respond/stop without force closing. I've restored all the way back to 17.0.5 and it still happens. I've even downgraded drivers with the same issue.

Especially an issue with 32bpc.

AE 17.0.5 and later (i believe all later but haven't tried all)

WIn 10 64
i7 5930K
32gb ram
GPU 980TI
Also happens with 2x980TI + 1x 980

Doesn't happen on my Razer 2019 Laptop w 2080

This is happening to me as well and I have a theory on what's causing it - if you are working in full resolution on a 4k project, and the comp viewer scale is at 25%, the comp viewer falls behind struggling to downscale each frame from RAM.

The info panel can say it's playing at real-time, but it actually isn't due to the extra time spent downscaling and I think this causes a desync. So let's say RAM is running real-time and you press space while it's at frame 50, but the comp view hasn't even gotten to frame 30 yet: the input gets delayed until the comp view catches up to frame 50.

This delay grows the longer you let the preview run, and gets worse the smaller the comp viewer scale is. So the delay until your input is finally recognized could be seconds to minutes long depending.

The workaround is to lower the preview resolution or only preview at 100% scale

Yep, same thing. I'm just doing the first tutorial and I'm getting this problem.

Mac Mini Late 2014
3 GHz Intel Core i7
16 GB 1600 MHz DDR3
Intel Iris 1536 MB graphics

Using macOS Mojave 10.14.5,

After Effects 17.1.4

Yep, same issue.

iMac 5k, 27-inch
Processor: 4 GHz Quad-Core Intell Core i7
Memory: 32 GB 1867 MHz DDR3
Graphics: AMD Radeon R9 M395X 4 GB

Using AE 17.1.4

If I'm editing a large 4k comp it freezes and is unresponsive and keeps looping. Sometimes I can press spacebar or click the timeline to pause it but most of the time I have to close the app.

I can't preview my work so this makes AE useless.

Fix please Adobe!!!!!!!!!!

Programme becomes laggy and a lot of the time unresponsive during playback. I can start playback on a section and then it won't stop (clicking the playhead, clicking button in Preview menu or hitting Space)

After Effects CC 2020 17.1.4 (Build 37)
Macbook Pro 15" 2016
Processor 2.9GHz Quad-Core Intel Core i77
Memory 16GB
Graphics Radeon Pro 460 4GB - Intel HD Graphics 530 1536MB

Same here. macOS Catalina, Adobe 2020, can't stop RAM preview without force close. Making After Effects completely unusable. Have to go back to 2019 until this is addressed.

One tip that might help is that when I switch to different application, that'll stop to ram preview in most cases. So command+tab on a mac will at least break this cycle of madness for me.