Underlying row sort logic


Can you help me understand the underlying logic of how the rows are sorted and why it changes? My understanding was that the rows were supposed to stay sorted once we saved the sheet until someone else changes it, but that's not the case. I'll be messing around in the sheet in the middle of the night when no one else is touching it, and it still changes frequently. I see there are years of complaints about this issue without a satisfying fix beyond the workaround of using reports. But if I don't see where anybody has really explained why it happens.