Are you talking about a six-story building that's clearly shifted, or did the ground just settle a bit? Either way, it's serious - when a house loses its vertical alignment because of flooding, it means the soil under the foundation has been washed away or settled unevenly, and the structure is experiencing abnormal loads.
The residents need to urgently call engineers to inspect the load-bearing structures - cracks in the walls, warped door frames, pipes and wires that are bending - these are all signs that something could collapse. In the worst case, the house could be declared uninhabitable and evacuated. In the best case, expensive foundation repairs will be needed (lifting the building, soil cementation, installing new supports), but that doesn't happen often because it's costly and technically complicated.
The main thing is not to ignore the problem. If visible deformations are there, you need to contact the administration, the housing authority, and emergency services to officially document the condition and get help if the house is deemed unfit for habitation.