Sorry Andy, just seen this so thanks for point it out. I'm amazed at how much the tile has bent without it breaking completely.
I haven't read the full thread in detail but have skimmed over it so apologies if I have simply repeated anyone.
Ok, so yes the paint was a very bad idea. But regards to the movement joints in the corner, although they should be siliconed, i don't think it would have made much difference. A tiny amount maybe, ultimately it still would have failed.
The main thing that Norcros would have been better off mentioning at the time..... As others have said about the depth of adhesive, the thicker it is the more shrinkage in rapid setting adhesives will occur. The Uniflex is a C2F and is only designed for a maximum 6mm final bed depth. Norcros say it can go to 10mm but only in small isolated areas. Based on the images it is 10mm (or more) everywhere. The only reason you would need to go that deep in one hit is if the wall was so far out of true of if there were dents that needed filling, but if that was the case, it would be best practice to correct the wall first before attempting to tile it and aim for a thinner 3mm full coverage.... unless you had an adhesive designed for much thicker beds.
Jobdone has hit the nail on the head as to why the curling happened, the adhesive gripped the paint, but the paint didn't grip the plaster. However at that increased depth bed, even with a correctly prepared surface, I would still put money on a class BIII lightweight ceramic tile cracking under the stress of the rapid adhesive shrinkage. A BIa porcelain tile may be able to withstand it far better and eventually settle but tile type alone would not be a reason for such a vast depth.
Unlikely the tile is faulty, it just has a very low biscuit density so could bend to some extent, but as I have never seen a tile bend like that in 20 years, I would be interested to find out how that happened without shattering into lots of small pieces.
