My 18v ryobi cordless drill does not hold a drill bit even tho i hold and tighten the chuck with my hand. It will hold for a wile but will eventually fall out. Thanks

Make sure the screw for the chuck (down inside
the chuck) is tight this happened 2 me. Brought it back
2 h/d The clerk played with it and the chuck screw fell out.
They replaced the whole 4 pack instead of just the drill.

Abrupt stops can loosen the ratcheting chucks. Before the invention of those chucks we had the ones that required a key. The proper way to tighten them is to alternate between all three position in order to "seat" the jaws on the bit evenly.That all but guaranteed it would not come loose I assume you have a ratcheting "one handed chuck". ther's only one way to tighten them and you don't get the same grabbing force. The only thing I can suggest is to try to eliminate abrupt stops or try cranking it tighter.