Opening a project that uses effects you don't have installed can trigger "Unexpected data type" or property creation errors. Step-by-Step Fixes 1. Identify and Remove Problematic Scripts
If you downloaded a preset from an external site, check the creator's documentation. You may need to install an auxiliary installer to define the underlying controls before using the preset. 5. Verify Script Syntax Match Names (For Developers)
The "Asked to Create Unknown Property" error is a common headache for Adobe After Effects users. It usually pops up when the software encounters data it doesn't recognize within a project file. This often happens when moving projects between different versions of After Effects or when using third party plugins. If you are stuck with this error, here is how to resolve it. Understand the Cause Opening a project that uses effects you don't
or scripts running in the background can trigger this error during startup. Corrupt Preferences
If you're on an After Effects Beta build and get an "Unexpected data type" error, delete specific folders: You may need to install an auxiliary installer
Ensure any third-party plugins (like Boris FX or Mt. Mograph) used in the project are installed and up-to-date. Rename Problematic Items: Avoid using system-reserved words like "Menu Type"
Instead of one massive expression, break complex expressions into smaller chunks. It usually pops up when the software encounters
Select your problematic .aep file and import it as a standard asset.