Originally Posted by shuffles
I can see that for the ones on the ground, as it was "cold" for a few days this past week. The other one was on the second floor of a building, not when it was cold.....

In november it was very cold here, for a while. That was probably when the loosening occurred, then slowly but surely the adhesive between the floor slab and the tile will have been getting weaker and weaker until .... POP.

It is something to do with the fact that typically the tile layers here do not lay down enough thinset adhesive (should be 1/2 inch thick) and because they rarely put in expansion joints to allow the tile to move a little during temperature fluctuations. Because the tile can't move (hits the walls) it gets jogged loose instead of expanding and contracting.