Sorry to bother you further !
According to the home page of your site, you are currently in "publish by issue" mode. Your author index page seems to indicate that some articles were published individually in "by year" mode before the journal was switched to using issues.
As corrected in my post later on, we published from the beginning in mode : "As part of a volume alone, by volume and year designated", this has, as far as I remember not been changed.
In the author's Index page, the two first articles in "S" went through the "whole" submission, reviewing and editing process, while the 3 next ones (test, test2, test4) are just 3 test submission examples not accepted and not gone through editing process: this to show you how they appear in that page, but not in the volume issue.