Concrete slab floors are super susceptible to the forces of nature. It's the slabs that form below it that can be a problem. Contractors can also build concrete over poor-compacted soil, which results in cracks and uneven concrete.
The first indication of problems is a crack in the floor. Once this starts to appear, the concrete will slowly sink over time. It's not just the floor that needs fixing either but also filling in the void. Leaving it longer increases the cost of fixing it later on.