I'm having problems with my stacks as well. Every time I try to click "Save and Finish" after editing one, I get a message saying "Error occurred during submission" or something like that. So I can't really edit my stacks.
This is my exact experience.
Also, I have a bunch of games listed in my stacks that appear as their Japanese versions despite their American boxart/gamespaces being present on the site. Can this be fixed as well? I do not own any Japanese titles.