Also, I don't know if this is related but the command will copy any new files over, but won't delete folders/files on the backup drive that have been removed from the source.
It's a hidden folder, in the root directory of Disk A. So I guess its path would be "/Volumes/Disk A/.Trashes"... Forgive my horribly basic understanding of unix!
You have excluded the .Trashes directory but not any of the content that it contains. When a user puts a file or directory in the Trash from a mounted rw device the file or directory is moved to the .Trashes directory on that device. The OS creates a directory within .Trashes named with the user's uid with the content to be trashed. So, either create mutiple PATTERNS or unlink everthing inside the .Trashes directory before runnning rsync.