After Effects Media & Disk Cache Corruption Diagnostic Guide

Playback degrades after warm-up and renders fail with generic errors

After Effects projects that play smoothly for a few seconds then stutter, drop frames, show gray or missing preview frames, and eventually throw generic render failures such as “could not complete command” are often suffering from Media & Disk Cache corruption or misplacement rather than a bad project. The useful takeaway is to isolate the cache layer first: if disabling Disk Cache stabilizes playback, the problem is cache state, location, or rebuild behavior, not the footage itself.

Media & Disk Cache is After Effects’ on-disk preview store. Disk Cache holds rendered frames for the current session, while Media Cache holds decoded media indexes. Both are written to a user-controlled folder. Mercury Playback Engine is After Effects’ render pipeline; GPU acceleration within Mercury can interact with cache writes.

Recognizable condition

• Playback is smooth at first then degrades to stuttering and dropped frames within the same composition.
• Preview shows gray or missing frames even though the source footage plays in the viewer.
• Renders fail with generic errors and the Media & Disk Cache folder grows abnormally large or stops growing despite continued work.

Cause to symptom table

Ordered checks

1. Confirm cache drive suitability. In After Effects open Edit > Preferences > Media & Disk Cache on Windows or After Effects > Preferences > Media & Disk Cache on macOS. Note the Disk Cache location. Required check: the path points to a local SSD with adequate free space and is not a network share, external USB drive, or a drive with aggressive power saving. UI labels vary by After Effects version.

2. Test with Disk Cache disabled. In the same Preferences panel uncheck Enable Disk Cache, restart After Effects, and open the problematic project. Compare playback smoothness to cached playback. Risk: previews will be recomputed each time and performance will change.

3. Clear and observe rebuild. With a suitable local drive selected, use Preferences > Media & Disk Cache > Delete Disk Cache and Delete Media Cache Files. Allow a short preview session and monitor the cache folder size and file timestamps to confirm new cache files are being written.

4. Isolate project-specific corruption. Create a new test composition with the same footage and effects from the failing comp. If the test comp plays cleanly, the issue is likely composition-specific, such as a plugin or expression.

Fixes tied to findings

If playback improves with Disk Cache disabled, clear the cache and allow a controlled rebuild on a suitable drive. Clearing forces full re-caching, which increases initial playback and render time.

If space is low or the drive is slow or removable, relocate the cache to a fast local drive via Preferences, clear existing cache, and rebuild. Do not store Media & Disk Cache on network shares, external USB drives, or drives with aggressive power saving.

If GPU-related symptoms appear, toggle GPU acceleration in Edit > Preferences > Previews > GPU Information. Test with Software Only playback to confirm stability, then re-enable GPU acceleration and test again. Disabling GPU acceleration changes performance characteristics and may mask underlying driver issues rather than resolve them.

If a specific plugin or composition triggers errors, render that section with the plugin disabled or pre-render it to an intermediate codec. Consistent errors point to a specific plugin or footage file.

Verification

• Open the same project with Disk Cache disabled and compare playback smoothness to cached playback.
• Monitor cache folder size and file timestamps during a short preview session to confirm new cache files are being written.
• Render a short 5 to 10 second segment after applying a fix and verify output matches expected frames without errors.
• Check Preferences for Media & Disk Cache location and confirm it points to the intended local drive with sufficient free space.

Escalation criteria

Escalate when the project fails to open or autosave files are unreadable, crashes persist after cache reset and safe mode launch without third-party extensions with Disk Cache disabled, consistent errors point to a specific plugin or footage file that cannot be replaced, or render failures occur on multiple machines with the same project.

Limitations and cautions

Cache location and UI labels vary by After Effects version, so preference paths may differ between releases. Clearing or relocating cache forces full re-caching of previews, which increases initial playback and render time. This guide assumes well-established After Effects behavior and current verification is recommended for version-specific preference locations.