The error is almost always script‑related. Note when it appears:
| When it happens | Likely cause | |----------------|----------------| | On opening a project | Missing or incompatible effect / plugin | | When running a script (e.g., animation presets, text scripts) | Script uses an old or wrong property name | | When adjusting a slider/checkbox in a MOGRT or template | Corrupted Essential Graphics property | | After duplicating a layer | Expression referencing a missing property path |
After Effects uses cache files to improve performance. Sometimes, these caches can become corrupted. The error is almost always script‑related
A surprising number of "fix" errors trace back to corrupted fonts or bad JavaScript expressions.
Pro Tip: While in Safe Mode, immediately go to File > Dependencies > Collect Files to create a clean copy of your assets without plugins. After Effects uses cache files to improve performance
If you are running a complex script (like DuIK, Limber, or Plexus) when the error appears:
When working in Adobe After Effects (often when copying and pasting keyframes, using expressions, or installing third-party scripts/plugins), you receive the following error message: If you are running a complex script (like
"After Effects error: Asked to create unknown property of type [Property Name]."
This error usually prevents the action from completing and may sometimes cause the application to become unstable or crash.
Since this is an expression error 90% of the time, you need to find the rogue code.
Given that plugins cause ~55% of "fix" errors, this method succeeds for most users.