Sloshy eggs.. I haven't heard this term and when i candled a few days back I found it a little odd how one kind of sloshed about as I rotated the egg.. This means the baby is dead? I thought something was wrong..
		
		
	 
What you are seeing when you turn the egg, is normal for a raw egg or a chick in early development (but not after the first week or so, as the chick should be filling up the egg more). The egg yolk is suspended by the 2 "bungee" cords called the chalaza. These fibrous cords keep the yolk centered in the egg and cause the yolk to always rotate so that it remains at the top of the egg, closest to the hen, whenever the egg is turned. The hen turns the egg to keep the yolk from sticking to one side while the chick is growing (which would be a disaster), but the yolk always ends "sunnyside up" keeping the developing embryo nearest the hen's heat source during the most crucial stage of early growth.
 
As the embryos develop, they fill up more and more of the shell so that the don't "float to the top" any more. Instead the chick will move and turn inside the shell until a few days before hatch the chick turns into the hatch position so that the head is nearest the air cell (fat end) and their beak tucked under their wing and tipped so that the egg tooth is close to the shell for pipping.
 
I'm not sure who you quoted with "sloshy" eggs, but if it was me you quoted, then I am referring to when the egg has decayed, and some gasses build up inside...when you gently shake the egg there is a distinct "slush/thud" sound and feel...a sure sign you have a rotten egg. (All eggs slosh if you shake them fairly hard...it is one way to tell the difference between a hard boiled egg and a raw one...try it sometime to see the difference.)
 
I only observed this at the end of hatches as I never shake a developing egg for obvious reasons. I only do that if the eggs are overdue and all I am seeing is dark when I candle. That is when it is hard to tell if I've got a live chick who is a late bloomer, a failed hatch chick dead in the shell, or a blob of mess. Since a chick fills up the whole shell such that it does not slosh like the raw egg, you won't feel anything move in the shell if you shake it similar to the feel of a hard boiled egg. .I'm not sure if the egg is a quitter that has putrified or something never developed...I tend to think a chick had formed, grew about half way, and then died to create that kind of sloshy mass. If you open the egg (carefully inside a baggie), it will pop and explode dark green gunk.
 
You can see the parts of an egg and the develop of the chick from this video (a favorite I share with my students when I have got chicks developing).
 
Lady of McCamley