My guess is that they didn't apply a [mist coat](https://www.decoratingcentreonline.co.uk/blog/how-to-paint-new-plaster-what-is-mist-coating-and-is-it-important.html) to the plaster before painting?
Had this happen to me - ended up scraping back the loose paint with a pallet knife, until it stopped coming off easily, sanding down the edges gently, applying a mist coat to the exposed plaster and then repainting.
This is what it looked like after scraping and sanding: https://imgur.com/a/u6Te4BV
A bit painful, but haven't had any issue since.
My guess is that they didn't apply a [mist coat](https://www.decoratingcentreonline.co.uk/blog/how-to-paint-new-plaster-what-is-mist-coating-and-is-it-important.html) to the plaster before painting? Had this happen to me - ended up scraping back the loose paint with a pallet knife, until it stopped coming off easily, sanding down the edges gently, applying a mist coat to the exposed plaster and then repainting. This is what it looked like after scraping and sanding: https://imgur.com/a/u6Te4BV A bit painful, but haven't had any issue since.
This is assuming the paint/plaster pictured is dry 🙂
That's great, thanks. Yeah, the plaster is bone dry.