Egg making crackling sound when candling

[Erin80]

I’m posting a lot but I have all sorts of weird things going on here!
Day 23 today. I see no movement in one egg when candling, but when I tap the egg it makes a crackling sound. Is this about to explode? Or is that a chick moving? No internal pips, but air cell looks good. No movement either though.

 

[Criticalicious]

Chicken egg or duck egg? At Day 23, a chicken should be hatched already.

 

[Erin80]

Chicken egg but temps were low so they just started hatching yesterday.