Paint peeling?

[ben100]

I’ve got this paint peeling while rolling so I’ve scraped back as much of the loose material until the edges seems strong enough. I’ve got some Zinsser peel stop, do I just apply it on the edges & mist coat the middle or Zinsser the whole patch? Also I’ve heard about filling it, what exactly am I filling & at what stage do I apply it?

 

[Wayners]

Ceiling or wall?
Solid or plasterboard?
Lack of insulation so it's a cold spot so condensation forms at that spot?

I would use toupret powder to fill as is.
See what happens.
180 grade sandpaper on some flat wood and sand smooth.
Give it a mistcoat of emulsion and see what happens.

Other option is to use peel stop around the edges
Then fill and sand. Paint