The big one was the .cargo/registry directory under the uid's home directory in the docker container. I also ran into the same issue with your sonarr and prowlarr images from yesterday.
I dug into it a bit more and it looks like the issue was a ton of hidden cache files that were included in the image that just took a couple of hours to get through chowning. The image on dockerhub from 2 weeks ago is 477 MB, and the image that was uploaded yesterday is 1.07 GB.
I just upgraded to the latest docker image (hosted on dockerhub) and noticed that the image size has ballooned to over 1 gigabyte and it's taking forever to start the container, is this right? It looks like it's hanging up on the chown command...