I have the same problem, maybe caused by new NVIDIA Studio Driver 442.92.

Comp with even only 1 layer, when RAM Previewed will cache, play back and when, during playback, I hit Numpad 0 again to stop, it doesn't. Comp timeline has focus (blue outline) but it behaves like I'm in a different window, not respecting the Stop request.

Windows 10
After Effect 17.0.5 Build 16 (tho this has been going on for several releases)

This is also happening with Mac.

This is very unique.
Create a composition, let's say HD.
Switch to 32bit mode.
Turn the composition viewer exposure control on - set the little exposure icon to any value, lets say +1.
Now this happens at different zoom levels depending on composition resolution, but if you're at 50% now if you press space to preview the comp, it works. You press space again and it stops.
But zoom in to 100% maybe 200% and press space.
The preview starts but you can't stop it. Pressing space, esc or anything other doesn't work.
Here are the requirements:
- 32bit
- viewer exposure turned on
- space preview
- a certain zoom level
Changing any of these "fixes" the problem.
You can switch to 16bit, turn exposure off, launch the Shift+Space preview or Numpad0 preview or just zoom out. Any of these will make the comp work properly again.
I was not able to reproduce it in AE 2019.
I have seen the "hand" cursor a couple of times so it seems it's something with the keyboard event. AE doesn't register the space ever being let go, that's why no other keys are working.

Hi Jason - Yes, please contact me with any questions! Thank you!

Hi Christopher,

Thank you for the posting this along with some details. We are actively looking into this issue.

May we contact you at the email address associated with your account if we would like to collect more information?

Thank you,
Jason

Bug Report:

When doing a RAM preview, After Effects will cache and play like normal, but won't stop. The interface will hang and AE will continue to play back indefinitely. This issue occurs seemingly randomly several times throughout the day.

This is occurring on several computers running Windows 10 and AE 17.0.4.

LENOVA P720
Windows 10 Enterprise 64-bit (10.0, Build 17763) (17763.rs5_release.180914-1434)
Intel Xeon Gold 6134 CPU @ 3.20GHz (32 CPUs)
128 GB RAM
NVIDIA Quadro P5000

Thanks Paul.

Could you provide more details on your system please?

Doesn't stop playback immediately when pressing the Space bar. Instead, there is a several second delay before playback stops. That never used to happen. This started after I updated to the latest version, 17.0.1. Please fix.

RAM Preview causes entire program becomes unresponsive to clicks, spacebar, Num0, ESC, etc. Playback continues on loop and the only way I've found to regain control is to minimize/maximize AE.