After Effects Error Asked To Create Unknown Property Of Type Now

Use PropertyGroup.addProperty() with a known match name or display name, or create via PropertyGroup.property("ADBE...") . 4. Expression trying to create properties dynamically Expressions cannot create new properties permanently. If you're trying to write a custom value into a non‑existent property, AE will throw this error.

if (layer.hasOwnProperty("sourceRectAtTime")) { // safe to use } When using ExtendScript ( app.project.item(1).layer(1).property.addProperty(...) ), you must use a valid property type string. after effects error asked to create unknown property of type

"ADBE Mask" , "ADBE Effect" , "ADBE Paint" , etc. Wrong: passing a custom string that AE doesn't recognize. Use PropertyGroup