Paper-backed solid vinyl papers are about my least favorite of all papers. The main reason is that they tend to curl at the seams, especially when there is humidity present.
The issue is that, IMO, the gritty manila-type paper backing is porous, and so it will pull moisture and humidity out of the air when the room is under humid conditions (teenagers taking long hot showers). Once this happens, humidity / moisture can enter the seam and soak into the paper backing, the vinyl surface can delaminate (come apart) from the paper backing, causing the surface to curl away from the substrate / backing. This is what you see in the photo.
Because the two layers of the wallpaper have actually come apart, it is also very difficult to paste back against the wall. It would be far better to remove all the wallpaper, properly prep the surface (smooth, primer), and then hang the new wallpaper.
The Wallpaper Lady's Blog 