There really is no reason to candle under lockdown. So if what is working for you is working for you, then no reason to change it.
Opening the lid briefly to remove dry chicks should not affect the hatching chicks significantly though, so probably not the reason you were having issues.
I'm trying to be philosophical about it, figuring that as I move my flock forward the chicks will be descended from those that DO hatch well.
Obviously, the story of Slowpoke reveals that there was something less than desirable somewhere in the flock (though the mother has now been sold to someone as a pet/eggs only flock where the new owner has no intention of hatching or breeding).