SpamSieve 'Good' Emails not staying 'Good'

Certain emails that I am receiving that could be considered ‘SPAM’ (emails from stores, etc) that I have told SpamSieve are OK (gone into the Message menu and selecting ‘Spam Sieve - Train as Good’) are continuing to be declared as SPAM when further emails are received.

It’s not that huge of a deal, the quantity of messages in my SPAM folder has decreased, but it’s kind of annoying to keep having to ‘train’ SpamSieve on certain email to no avail.

TIA!

Please see this page for how you can see whether this is happening because of SpamSieve, and send me the report via e-mail if necessary.