This may have been fixed in the latest versions, but in version 4.1.13, the Shopping Cart Signup form seems to have a bug. When you try to delete the products that are in the basket, you can only delete one at a time, if at all.
Please upgrade to latest version - 4.1.15 , it solves this and many others problems. I believe it is not good idea to submit bugs into bugtracker if you have not-latest version running. What is that is already fixed?