Golf Ball Test
Tile Tenting is when tile breaks loose from its base, sometimes it 2 pieces lift to look like a tent. Other times the grout stays black weeks or months after it was wet.
Take a golf ball or a wooden broom handle then tap on the floor. Healthy tile sounds like a bat hitting a baseball. A hollow sound indicates there is an air pocket between the tile and the floor, Tile failure. Bacteria begins to grow in there and the problem will spread unless you perform a tile repair.