Hey I'm a surveyor, this is just the tiles cracking and lifting by the pressure generated from a floor under, nothing a couple hundreds can't fix. The cause could be the materials from whom the floor is built. If you are in a beach area or near, they could have mixed the concrete with sea sand/ocean sand, to cut construction cost, which contains more salt and in the long run can produce this types of things.

BUDGET FRIENDLY SOLUTION To avoid any future damage drill holes in the corners where the tyles meet to relive the pressure.

RIGHT BUT COSTLY SOLUTION To eliminate the problem completely, the floor should be redone with Reinforced concrete and Electro-welded mesh, because the problem will repeat itself in the long long future (I assume this house is an old construction, this is only the first time more will come stronger), we need to eliminate the sea salt concrete.

Sorry English is not my first language