Flaking/bubbling plaster/plasterboard...?

[KiloBravo]

So I'm not sure what exactly is going on here but as a picture is worth a thousand words I've attached.

Hoping to get an idea of what's wrong/failing and what would need to be done to fix it?

Would very much appreciate your thoughts.

 

[opps]

It may water ingress from outside.

Can you take photos from outside?

If it is ingress, you need to deal with that before trying to sort the inside.

 

[KiloBravo]

It may water ingress from outside.

Can you take photos from outside?

If it is ingress, you need to deal with that before trying to sort the inside.

Didn't think of that.

Some pictures attached.