I've read they waddle, like penguins It's very painful, the poor things. The muscles are contracted and trying to expel. If you've ever seen a hen laying an egg, you'll see her "stand up" just before she passes the eggs, when she's straining and grunting. That's the standing position they are fixed in.
With my soft shell layer, she, uncharacteristically, would sit on the ground and looked tired. Laying a soft egg is much harder and taxing on them because they have no hard shell to push against.
Do you offer crushed oyster shell free-choice?