I have done a lot of this kind of work. I would say your main problem is probably glue left over from the wall paper although I cant be 100% certain. How I prevent this from happening is skimming the entire wall with durabond. I can't say it enough, but durabond is a life saver in most situations and is a far superior compound then the rest. Skimming an entire wall or house can be time consuming, messy, and just a pain.... but in most cases it is what ensures the best finish. If you skim the wall and it bubbles, just poke at the bubble and knock it out of the wall and skim back over it. You may have to do it several times. But I can tell you with 100% certainty, if your texture isn't sticking it is because there is nothing for the compound to adhear to, or the water in the compound is messing with whatever is left behind from the wallpaper.