New plaster blown - please help!

[Appleandabanana]

Hoping someone may be able to help me! Had the walls in my 1910s property skimmed a couple of months ago and now have approx 10 very long vertical hairline cracks along them. The areas around many of the cracks sound hollow. The plasterer has said that this has happened because the walls are old and that he will fill the cracks but not replaster. I’m now wondering if the walls might have been painted with lime wash or something which meant the plaster didn’t stick. Anyone with any knowledge of this? The photo is of the walls pre plaster.

If the walls were lime plaster they should really have been repaired with lime to maintain necessary breathability. Gypsum over lime almost always fails in various ways.

Could it just be expansion and contraction due to heating?

That looks like damp. Could it be damp coming through the plaster?

Was the plaster below blown before they skimmed it?

This

@Scampuss not sure if original plaster was lime plaster, it was white and painted as per the pics.
@ThickButteredToast surely it’s not normal for a skim to debond so soon, even if there have been temp changes?
@thechangling no damp
@Geneticsbunny original plaster wasn’t blown

Your photos aren't really clear enough to see what was going on, but it looks very like old lime which was 'painted' in the past with either limewash or distemper, as would be typically for a house of that age.