Hello all
Has anyone seen plaster do this???

Our internal walls show some cracking 2 years after replastering. The
worst has three long cracks up to five foot long, which gives and
bends in on pressing.

Here's the good bit. I removed a small piece of plaster at the centre
of the cracking, and could poke my finger in about 2 inches to the
plasterboard underneath. A 6 foot square area of plaster has come
right away from the plasterboard underneath!!! No wonder it's
cracking, it's supporting its own weight and only gripping the wall at
the edge of the area. Presumably it's still coming away and will fall
off.

Can it be PVA'd back? Some other adhesive? Was there some cheap crap
substitute used in the plaster? Should we just have it redone (by
someone without a wide hat and stirrups)?

Any advice from you experts appreciated!
Adam