I have this happen... usually in my forced air bator. Got my best hatches in still air.
I feel like the reason this happens is because of differing egg shell quality... and I THINK the sticky chicks are starting with more fluid inside their hatching egg... maybe unabsorbed albumin...

I have NOT selected for shell quality to be the same or at all yet.
Makes me crazy to get a chick with it's wing glued to it's head or shell glued to it's back... NEVER had that issue in my still air hatcher, almost EVERY hatch since using forced air though... and JUST like you NOT all of them.

It has changed my "help no one hatch" policy, since I feel like they are fine but I did something.