What is your current nest box set up? how many boxes are there? Are they moveable? If so, you could move them to "shake things up a little" to get them to reset their routine. Or you could block the one they seem to be crowding into. Then they might decide to use the other ones. They might, I say, because some can be rather stubborn.
They started laying in this box even though both boxes had golf balls in them. I had to remove the golf ball from the one they all lay in because the eggs would crack against the golf ball. The other box has had a golf ball in it the entire time but they don't give a 'squawk' about it. I'll try blocking of the favorite nest box to force them to go to the other to lay but I don't what will keep them all from laying in that 1 box. (same problem) They are so cute, its almost has if they have a schedule worked out among them - to use the one nest box. I feel so silly.
You should keep doing what works for you. Maybe my girls are just clumsy, the broken eggs don't happen everyday. Just enough for me to be concerned. I definitely don't want them to start eating the eggs. Maybe I'm just overreacting. I'm new at this.
I have a 4 foot area for them to lay in. Make shift nest boxes. 3 have picked the Lt hand corner and 1 has picked the Rt hand corner. A 5th hen that always layed on the Lt side of the previous hen house and just started laying again, also picked the Lt box. Why? I don't know!
I have 3 double wide nest boxes in my coop and the 10/12 layers all lay in the same side of 1 box. Makes for an easier collection, and I haven't had any breakages yet. My only problem has been the bottom pullet was pecked and forced out the other day, quite a bit of blood on her comb. So yesterday when I did the coop clean-up I put fresh hay in each nest box and a few fake eggs I picked up at the store. We'll see this morning when I go down if it worked.