Paving pushing up because of the hot and super dry weather

I would love to hear if anyone has had an experience of paving being pushed up because of the hot and dry weather this summer.
We have had a number of patios where this has become a problem (a couple we laid ourselves and quite a few more where another landscaper has laid the patio. )
All our patios have been laid with 100mm subbase layer and then laid on a full sand/cement bed. the back of the paving has been primed (infact most of the slabs are still stuck to the sand/cement base)
One patio was limestone, laid in Feb this year. another one porcelain. The porcelain one was grouted and the limestone had a flexible point.
Something similar has also happened to a sandstone patio laid a couple of years ago. All of these patios were fine until July and then the problems started. Theris also usually a crack running through the concrete layer underneath.
I'm trying to work out who is liable and what is causing it. After quite a bit of research I think it may the the clay underneath contractiing and cracking the concrete but I can't be 100% sure.
We will now have to fix these patios when the weather has cooled down, but I have not accepted liability yet because the patios were fine for the first 6 months before this issue occured.
Has anyone else had a similar experience.
Many thanks
Will