Interior Concrete slab floors, including basement floors, are susceptible to moving just like outdoor slabs. Shifting soil often creates voids below the concrete. Not to mention, concrete can sometimes be poured over a poorly compacted sub-base or sub-grade causing uneven concrete.
A good indication is cracking. Once a crack occurs, the concrete will start to sink. It is important to fill the void as soon as possible because the longer you leave it, the more expensive it can potentially become.
Call DTC Concrete Levelling for a consultation and free estimate.