My Preview is broken somehow

[hatechan5CC4]

I'm using After Effect 21 and in one my certain project, which contains a lot of 3d camera and adjustment layers, does not render one exact piece of timeline. It just doesnt make sense for me, but after im starting playing this piece of timeline everything stops and moreover, it breaks the whole timeline after i try to preview this one piece. After i purge all the memory it kind of repairs everything, but this piece keeps to break the whole timeline again and again. My memory setting- 13 for AE and 3 for other applications.

[Vishu_Aggarwal]

Try the follwoing - 

• Go to File > Project settings > General > Video Rendering & PlayBack > Change to mercury playback engine Software only.

or 

Because your working with .m4v video files so go to > Preferences > import > Enable Hardware Accelerated decoding (disable this) and restart after effects. 

if this does not reslove your issue...gives more information -

1. If you off motion blur does it work ?

2. try changing the range playback to that section only and see if it works

3. Share the settings of the preview panel 

[Mylenium]

Hard to tell without any detailed info about teh project, your settings, your computer, but honestly, your timeline is rather messy. You may want to start by pre-composing the relevant segments so you don't have more than 100 layers on the timeline. That alone may fix the issue and prevent the rather apparent issues with GPU acceleration. Likely it simply breaks with the 3D text because the driver is outdated or your hardware not configured or compatible. The usual steps apply: Update the graphics driver, check the hardware acceleration settings. And again, seriously consider a bit of housekeeping.

Mylenium