Number of items does not match the number of keys

Hi All!

So I am just learning Dynamo and I am trying to recreate some dynamo workflows based on videos.
At the moment I am looking into image based curtain panels, but I can’t seem to make it work. I get an error saying that the number of items does not match the number of keys.

Curtain Wall based on image.dyn (28.1 KB)

I am attaching the file and the link of the video.

pls upload the rvt file and the image:)

On List.GroupByKey the length of the list should match the length of keys

Cant provide any further assistance without the associated image and Revit file
Also post a screen shot of your Dynamo graph with preview bubbles expanded.