Carpet is made in a certain order. The knap is running one certain way. Ideally when splicing, you always want the knap to be spliced together with the knap going the same direction. Some novice or unknowing installers twist the carpet around and have the knaps going in alternate directions and this will show up for a long time. Its like stroking a fine suede coat one direction and the adjoining the other. You see my drift.
but in the age of yours, this should have settled down. I would have it cleaned with steam and dried well, and then see what happens.