When I read this..I got the shivers as I could feel your frustration and hurt.
I have a big BO gal that was great on brooding but once the chick hatched...
She had loads of room so that wasn't her problem. One hatched and then next thing I would hear is a terrible crying/peeping sound. Checked and here this wee baby wobbling on its little feet by the door of the brooder cage, feeling lost and alone. Mom not 2 ft away sitting like nothing was wrong.

I took it out, got it warmed next to my skin, while I did that I checked under the hen.
I think baby went in that direction cuz another BO mom was hatching across the room and was talking to her new chicks. Baby just wanted to be included.
There was one egg crushed (as you had) and one that died as it was also crushed and could not get out.
I do not know why she did that, it was hot out and surely it was not to keep them warm...? If anything I would have thought she would have backed some what away from the eggs...
After I got the little one warmed I thought I would give it back to the mom. She wouldn't have it and proceed to peck at it, like it was some alien thing.
I thought alright, be that way...you just lost your baby!
I watched close after that and ended up having to help one hatch it was so dry. I gave all the babies to another BO mom. She was more than happy to add to her now hatching brood.
Sadly that was repeated with each hatch, she would ignore it or the baby would try to force its way under her and she would not lift to aid the baby. Then it would start crying. Thankfully they all hatched within a couple hours. I spent that time out there with them.
I still don't know why she acted that way. I wish I did as it was heart breaking to see.
The odd thing about it after, she didn't seem to miss her babies, much less want them.
Sry for long post.
Good luck.