JPH45 had his .38-55 loosen up in 1500 rounds IIRC, so it's not unheard of, the underlug does wear, it's much softer than the hinge pin and that's just from opening and closing the action, the pressure on it with the high pressure calibers also takes its toll on it. One good reason to use some lubricant on the hinge pin, I've used Tetra and also have treated a couple with Moly-Fusion. Another point of wear that doesn't get much attention is the spacer on wood stocked rifles or the breech end of synthetic stocks. If these wear, the barrel will be loose when the action is opened and POI will change as it wears. I use beeswax or paraffin on them to easy the friction.
Tim