Still I do not understand...then how do you explain the one that are not affected by competition (they remain static as soon as they do not have a date at the end of their listing), which means that google is not visiting them daily. As far as the site in question, it was 4th on 1st page, then the next day
10th, then 12th, then again 4th then now it is 12th without any date mentioned...maybe meaning that Google decided for another unkown reason to leave it there... so I do not think that competition is the main factor.
Thanks.