You created a Motion Graphics Template (MOGRT) or used the Essential Graphics panel. Sometimes, creating a "Master Property" and then deleting the underlying source (like a shape layer) causes this "unknown property" error because AE is still trying to create the Master Property link.
The is intimidating but rarely fatal. In the vast majority of cases, a third-party plugin or a single corrupt text layer is to blame. By systematically isolating variables—starting with Safe Mode, then plugins, then project repair—you can recover your work within 15–20 minutes. You created a Motion Graphics Template (MOGRT) or
Sometimes the newer JavaScript engine fails to interpret specific custom properties. You created a Motion Graphics Template (MOGRT) or