In my early case, around 25% are infertile and around 35% gone bad before day 20th.
For infertile eggs, I think they need a bigger pool for them to mate in the water. I watch a video for breeder, said in water avg. one drake can mate with as much as 27 hen.
I only had two drake and 20 hen. I do saw the shorter drake (Indian Runners) try to mate on the land and he droppd on floor twice. the tall one do better.
For those gone bad in the incubator I think because the eggs are dirty. So now I clean them all before put in to incubator. seem it work and the later 3 batch which still in the incubator are only 1-3 pcs turn bad, much less than before. Most likely the next few hatch could go up to above 50%.
Some eggs pipped & crack the eggshell, but did not break through a hole on the 2nd day after pipped. usually will die inside in the end.
Now, as long as I saw they start pipped but not through in the next few hours. I will use tweezer take out a small piece of shell & make a tiny hole right on the place which they pipped (in air pocket area like below picture 3 green eggs on the top, one of them start pip the hole bigger and bigger should totally break through within next few hrs).
And, the last 4 batch of hatch none of them die inside after pipped. those are in the earlier post last picture.
A week ago, I start to arrange duck eggs separate into one incubator with humidity 60% and chicken eggs to others with humidity 55%. I may try 65% later.