I have found that nests work best if sized for one hen. The problem is that we have different sized chickens, from various bandies to oversized giants.
The ban ties tend to sneak in beside a larger bird and then just irritate her until she gives up and goes looking elsewhere. (There will be no more banties when these are gone), although our best rooster is one. Great little guy, very protective of the flock, a true “gentleman! But had to get rid of two banty roosters this past summer, beating up the hens, total jerks!