Re: Tile - Adhesive or thinset?
It could be many things. You may have used the wrong type of tile, porcelain doesn't hold up well to traffic. The substrate may be uneven, causing a pocket under the tile. You may not have used enough adhesive to fully coat the back of the tile, leaving a portion unsupported. If on slab, the slab may have cracked and it's telegraphed through the tile. A pre-existing crack that wasn't addressed prior to the tile would cause the same problem. Whether replacing the tile will cure the problem or not will depend on what caused the problem.
I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!