blown skim

I booked my plasterer via checkatrade - he was really highly rated so I didn't question his methods. He applied primer to the wallpaper on the ceiling. Some bubbling/raising of the plaster has since occurred. Will the problem of cracks etc get worse as a result of not stripping the wallpaper...

Hi guys, I skimmed a painted ceiling and questioned if there was enough suction. The walls are glossy ish but. The ceiling seemed not too bad. Anyways, I used Wba on walls and just 2 coats pva as normal on ceiling. Walls are fine but the ceiling has blown. I 've chipped all skim off- used a...