We can trouble shoot the problem if you would like to post the details.
its generally flock, collection, incubator and hatcher.
What type of quail?
what type of food are they being feed?
what's the rough male to female ratio?
How many birds in the flock?
How many eggs per day?
What kind of floor are the eggs layed on?
Estimated age of the flock?
Any oversized double yoke eggs?
What's the weather like at the moment?
What's the feathers look like on the birds?
Any thing odd going on like death, lack of weight, etc?
When you collect are you storing them and if so how?
What type of incubator?
what type of turner?
Do you hatch in the same incubator?
Type of hatcher?
Whens the last time it was cleaned?
How many eggs do you have to remove because of rotten smell?
Have you tested the temp against more than one thermostat?
What humidity are you using during incubation?
what humidity are you using during hatch?
How many days since you set till they hatch?
What results are you getting including any candling or checking un-hatched eggs? (double bag then cracked to see what's inside the egg.)
I know this is a lot of questions but its the quickest way to work out where the problem exists.
If you have a lot of clears it could be as simple as to many males are stressing the females and knocking each other off while breeding. That would show up in the females having a lot of feather damage to the backs of the necks. If on the other hand you have a lot of late quitters then humidity during incubation would be something to look at. Hopefully with some details we can work out what's going wrong and why.