Hello Nick,
Thank you for contacting National Instruments.
I tested this out here on my computer and did not get the same error that you received. I have 2 nested for-loops that unbundle the contents of the clusters. In the outer loop, I unbundled the Edge Coordinate array, and in the inner loop, the X and Y arrays. Instead of manually indexing the array, I used the auto-indexing feature of the for-loop. This made it so I didn't have to specify the number of iterations for the loops.
The image attached to this post is a partial VI that shows the loop structure I used for testing. Not all of the required inputs for the IMAQ Rake VI are shown, but the loop structure definitely works. I also pointed to one of the indexed tunnels with a red arrow.
Each of the output arrays is two dimensional. Each column corresponds to one of the edges found, and the rows correspond to the specific points on the edge.
Hope this helps you resolve the error.
Best Regards,
Jesse D.
Applications Engineer
National Instruments