I have resolved the issue by installing a premium SEO plugin that checked all my back-links and picked up the culprit: an automated back-link rule that linked all instances of “website design” to the mentioned URL, thus producing the interesting (or rather normal) effect of one instance been deleted and automatically back-linking to the next one. I used Premium SEO plugin.
However part of the question remains unanswered which is: How this did happen? Since I didn’t created such back-link rule and it was created on July this year. No one has or had been granted access to my dashboard.
So if anyone experience similar issues you can always begin by checking any automated back-link rule that may or may not be created by you.
On the bright side I was relieved that the back-link wasn’t to a more obscure content website.
Thanks to everyone who took the time to view my query and more to those who offer advise.
Have a great year on 2018!
Regards
XS