Well.
Maybe. Lol.
What bator do you currently have?
Do you hand turn?
If you have an auto turner, is it vertical?
If it is horizontal, do you mark your eggs to make sure it is actually turning them, and not just pushing them in a circle?
What is going wrong, specifically?
Infertility, yolk adhesion, early losses, late losses, losses after lockdown....?
How old are your adults?
Are they purebred or a mix?
How clean are the eggs when you set them?
Do you clean them if they are dirty? If so, how?
I am happy w my HovaBator 1588 w vertical auto turners and a humidikit for incubating, and use the same set up without the auto turner as a hatching incubator.
My hatch rates are typically very high, 85/90+% w my a welsh Harlequin ducklings.
If your incubator doesn’t hold humidity well, that could be a problem - but may also be “helped” by using some cut up pieces of sponge to add humidity - they can be rotated (on a staggered schedule) to maintain proper humidity...
If you don’t have a secondary way to monitor temps, and a calibrated hygrometer.... that could also be your problem.
Many of even the more expensive bators are not properly calibrated on arrival.
Is there any chance your hatch rates might be low due to off temp/ humidity/ hot spots in your bator?
Also for consideration-
Heat can affect the fertility rates for drakes (and most fowl).
Different breeds of ducks also have higher/ lower typical fertility rates (so I’ve read, I can’t say that from experience)
If you are having low fertility rates,
....have you cracked some of your eggs recently to look for the “bullseye” to get a feel for fertility rates? (Pix attatched)