Check for Debris, Damage or Wear
Remove the neoprene seals and check them for debris, damage or wear. If the disc below the seal is dirty, try cleaning it with an abrasive kitchen pad, then rinse and replace it. If the seals are damaged, replace them. This may be all that's required to fix the problem. Reassemble the faucet and check for leaks.
Important: Before turning on the shutoff valve to check for leaks, first turn the faucet to the on position, then very slowly turn on the water at the shutoff valve so any trapped air escapes gradually. Otherwise a pocket of air might be forced under great pressure into the cylinder and could crack the discs.