I agree with
@JaeG for the most part. So many variables. I believe that some instances of sticky chick are likely due to circumstances beyond our control. You can't always control egg quality (or even handling, if you're buying hatching eggs). One out of a whole batch is probably just a fluke. Each egg has it's own specific variables, so we just have to try our best to meet the needs of the majority.
That being said, the only time I've had these issues was when my incubator was running a bit too warm. It was within the acceptable range, but on the high end. After exhausting myself with a zillion thermometers, I've figured out how to manage it. No problems since, regardless of humidity.
Everything I read pointed to humidity as the culprit, so I went so far as to experiment with dry incubation after my first awful experience with sticky chicks. It didn't help. Like I said, my temp was within the acceptable range, so I didn't consider it until I realized the humidity wasn't the issue.
If you had sticky chicks AND a low hatch rate, I'd definitely recommend checking the temp with a really good thermometer. Never ever trust the one on the incubator. I also have a hovabator, and I have to adjust it every single time I use it. It was very consistent for a few hatches, but now it's not. It still works like a champ, I just have to be more vigilant.