Bearing internal clearances are measured in tenths of thousands of an inch. Pump components can be damaged by vibration. Wear rings, bushings and impellers are three examples. Bearing seals are very sensitive to shaft radial movement. Shaft damage will increase and the seals will fail prematurely.
Labyrinth seals operate with a very close tolerance.
Excessive movement can damage these tolerances also. Pump and motor hold down bolts can become loose. Damaged impellers and non concentric shaft sleeves are common. A bent or warped shaft. Pump and driver misalignment.