Addle eggs

[Sandy]

Can anyone tell me what causes addle eggs I have 50 Mallard duck eggs in my incubator I had these from a breeder They were due to hatch today got 5 i think around 35 are addle What causes this and will they explode if left in the incubator

 

[Dipsy Doodle Doo]

Hi!
Addled --- like scrambled? Do the insides 'slosh' around?
My guess would be rough handling. Were they shipped eggs?
You got 5 ducklings? Congrats

The scrambled / addled ones aren't going to hatch (I'd've removed them when I saw they were bad), but I don't know how likely they are to explode.
I wouldn't leave them in the bator TOO long past hatch day --- could turn into a mess

Good luck,
Lisa