When you can do it, go to the command line and run this command rather than using the web ui so it doesn't hang if there is a problem:
/usr/local/emhttp/plugins/recycle.bin/scripts/rc.recycle.bin stop
It should only take a few seconds to return.
When I asked about your system being busy, I really meant the amount of disk activity. The recycle bin trash size has to hit the disks to determine the sizes of the .Recycle.Bin folders and if there is a lot of disk activity it can take a while. With the recent update, I've moved all trash size checks to the background in case any of this was hanging the UI. The downside is the trash sizes may show '?' if the trash size check times out, but I guess this is better than a hung up UI. That large rsync copy could slow down the recycle bin trash size check.