Get some PVA.....that is almost certain to work.Thats interesting, and annoying. I redecorated in here a couple of months ago, I noticed after the hot spell had finished that a section of paper on the back chimney breast had lifted, annoying, normally if I stick it down it stays stuck. I mixed up some more paste and stuck it down, looked at it the following day and not all of it had stuck down, I repeated it and again and again more had stuck down but not all, repeated again and the same thing has happened and I've still got a small edge that hasn't stuck down.
Did you size the wall properly before decorating ?