The yawning motion means it's still absorbing its yolk.
Signs I see, is the chicks start wiggling, & becoming more active. Within a few hours you should expect the chicks to chip shell at the edge of the pip. This is the beginning of a Zip.
But if they begin zipping, & don't go any further...
I had an incident this year. I got up early in the morning to check the hatching progress, & everything looked fine. Chicks were hatching, & pipping.
One chick in particular I saw it's beak sticking out of it's pip hole like it should, I sat down for a drink of coffee, came back over, to find...