Keep the humidity low all through incubation. Only raise it for lock down, once they internally pip. Otherwise you risk drowning the ducks/geese internally from running the humidity too high.
Weighing the eggs and candling are the best ways to tell how they are doing and checking weight loss for a successful hatch.
Our cabinet bator runs around 33% on a daily basis. We move eggs to hatchers where we can up the humidity as needed for lockdown and internally pipping.
If you are new to incubating geese, Pete's guide (sticky in the goose section) should be required reading to guide you during the month of incubation.
We can't be perfect in replicating mother nature, but then again nature isn't perfect either, and 100% hatch rates are seldom in nature.