The plaster has detached while knocking the grooves...

Hello, today I visited my construction site full of anticipation and have been somewhat unhappy since. What could be the reason that the plaster is coming off the wall? It surely can’t be just from the chasing, right?

Sorry, but that didn't "come off" and fall from the wall with the clean "diagonals." In the upper area, you can even still see traces on the plaster...

Sorry, but it did not "come off" and fall off the wall with the neat "diagonals". In the upper area, you can even see marks on the plaster...

The installer knocked off some of the plaster to check if it was firm. The marks are from the hammer!!! The stuff has come off on a large scale!!!!

The installer knocked off some of the plaster to check if it was solid. The marks are from the hammer!!! The stuff has fallen off over a large area!!!!

Really?! o_O Oh dear... What kind of plaster is that?

Really?! o_O Oh dear... What kind of plaster is that?

A gypsum plaster, as far as I know. No idea exactly what. I sent the company a notice of defects today and hope they don't have to remove everything...