Water damage is common in showers, bathrooms and entryways. The grout may have broken down, or the wrong grout may have been used. Water gets underneath the tile and damages the subfloor, causing it to expand. This is common if a porous backerboard was used instead of a waterproof cement board.
When a house settles, the rooms where it settles cannot be determined. It all depends on soil conditions. This will cause the tiles to buckle and crack. If this is happening in your home, you need to call out a professional to examine the foundation of the house.
Poor Original Layout
Occasionally, a room is not measured correctly, and this throws off the layout of the tile. If you live in an area where the temperature and moisture levels fluctuate radically, the walls may actually be causing the problem. They will expand and contract, and this pressure will force the tiles to pop up.
If the mortar is old, it will become loose. Normal walking on old mortar will cause it to pop up off the original surface. This may be more common around washers and dryers because the vibration from these units actually works the tiles off the floor.