Help! Turkey egg with weird development

[Keltceee]

This is my first time hatching turkey eggs. We incubated 23 eggs. 14 are healthy poults. 1 died in the last days of incubation, 1 died during hatch, and 1 had mushy chick disease and died, 5 were infertile. The last one I have no idea what is going on. At day 15 it was developing. By day 25 it looked like it had died. There were no veins, the air pocket was relatively small, and it looked nothing like the others. I decided to give it a few extra days to be sure. I checked on it again after all the others had hatched and dried, and it had two veins in it so I left it in the incubator. I have been checking it every 2 to 3 days since. I am now seeing more veining and the air pocket is growing slowly. This egg has no smell, weeping, and stayed warm when I did the 10 minute test. Yesterday the two black spots at the bottom appeared. Could it still be developing? These are the best pictures I could get, but the egg is not as red in person.

 

[SmiYa0126]

@Eggcessive do you know?

 

[Eggcessive]

I see eyes and veins, but I have little experience in candling.

 

[SmiYa0126]

Any update?

 

[Keltceee]

Any update?

The air pocket has grown some and a little more veining is noticeable on the top. However this egg is now 21 days past hatch. It still has no smell and no weeping. I am going to try the 10 minute test again later. I feel like the veins should have disappeared and it should have exploded by now if it was dead. I don't see how it's possible for it to still be alive and developing after this long.