As seen in the image, once when the world is loaded, there is a large lag spike as it is creating the item frames and redstone dust in my case, and creates 9 stacks of each for each item frame on the wall in a specific area. This is a map I have been working on and it didn't happen at all on the other side of the other side of the map that is 100% identical.

Left image has 12 item frames, thus making at least 216 stacks.