Guitar tuning machines, especially those open tuning machines, are gears that wear as time goes by. They might need some simple maintenance from time to time to make sure they function well. If the gears are clean of debris and lightly lubricated, they can last for a long time.
Take a small amount of high-viscosity bicycle chain oil using a toothbrush, toothpick, or cotton swab and apply it to the mechanism, the worm gear section. Turn the peg back and forth a little to spread the oil to the mechanism. Finally, wipe the used oil off the surfaces of the gears and worms.
The small amount of oil that is left on the parts is all you need. Don't need to over-lubricate guitar tuning pegs and don't lubricate with low-viscosity oil, because it will wick behind the plates and damage the wood and finish.