I keep manually moving one good email from the Junk Email folder by assigning “Train as Good” just to see it tossed in the Junk Folder next day. Since it is an isolated problem and on one particular email, I am sure there would be a solution right here. I am using SpamSieve 2.9.24 on OS X 10.11.4 (15E65). Incidentally the email that is wrongly sent to Junk Folder is from respectable technology aggregator ***What’s new on SlashGear.com ***under SlashGear sender.
Which mail program are you using with SpamSieve? Also, please see this page.
Outlook 15.19.1 (Office 365)
Did you check #5 on that page to see whether the messages are going to the Junk E-mail folder because of SpamSieve or for some other reason?