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NZ_Tiler
If the adhesive was XR7, it has a short pot life. Is it possible more water has been added to a setting mix to extend pot life? Causing weaker adhesion...( or skinned over to early) The adhesive also looks thick, I can't see on the spec sheet the maximum bed thickness, generally max 10mm. With a brick bond setout, excessive packing up may have happened to get tiles flush???
It's rare but some tiles are contaminated on the backs if you have a box spare you could check this and eliminate this as a cause.
It's rare but some tiles are contaminated on the backs if you have a box spare you could check this and eliminate this as a cause.