What have you been doing currently and are they your own eggs or shipped ones? Have your eggs been developing until almost the end of incubation, or have they been dying earlier in the process? What's your incubator set-up?
Tracking the eggs weight loss using a gram scale is a good way of ensuring you have the humidity set correctly. Eggs need to lose 12-16% of their start weight (more for fresh eggs, less for older eggs) by lockdown.