New emulsion on previously emulsioned and papered walls.

wet walls with hot soapy water scrape off all paint use zinsser gardz were requiered never use pva before painting only before lining

Well you had to use primer before emulsion. Any ways now to sort it out, Skimm/plaster the wall, then sand it to level and prime it, than emulsion.

Hi. From your description when the new plaster was painted it was not prepared correctly ( mist coated paint for new plaster) so the coating that is remaining is not adhered to the plaster. When it is activated by water (in the paint you are applying) it bubbles up due to being a film of paint that is just sat on the surface. I would wet the paint and what bubbles i would scrape off, i do this by getting 'behind' it with a very thin filling blade i use. Dry sanding will not resolve this. Once all the loose paint has been removed i would size the walls with pva mix (1:4 or 1:5) then line with 1000 or 1200 grade lining paper. Done correctly you will have a perfect surface for future emulsioning

Apply a coat zinesser gardz after the appropriate preparation. Then I would recommend lining them.