cracking screed at edges abutting patio doors

[Vchristina1]

Hi
I apologise if this has been posted many times before but I did try and search for the original advice but couldn’t find it
We bought a new build property and the screed is cracking - the builders came, dug it out and relayed it and it crumbled a matter of days later again even in dry weather (not wet conditions outside) they are now saying they’re stumped and don’t know what to do. Please can someone help/advise it’s really getting me concerned

 

[ktuludays]

It looks really thin, there has to be movement somewhere for it to break up like that

 

[dazlight]

Your Dpm sheet is ripped and there is a void so it needs digging back a few inches. The sheet repairing then making sure no air pockets behind it then fill in with rapid repair.

 

[ted456]

Is this a conservatory?
How high is the door sill above the outside ground level?
There's damp showing on the screed surface.
What's under the membrane?
Hard to tell but the screed looks like SLC? Is it SLC or S&C?
What exactly did the builders dig up - the whole floor?

The membrane is wrongly laid, & appears to be in the wrong position - somehow, moisture is getting under the screed.
The screed is far too thin, & shouldn't have been laid direct on a DPM.
If the whole of the screeded floor is like you show then the whole floor stands a good chance of crumbling.