Looks to me that she was trying to escape and just reflexively pecked the egg that was there.

Are the hens getting enough calcium in their diet?

I'm going to chime in with the calcium crew. I keep a little feeder filled with oyster shell and quartz grit mixed together for my hens all the time. My hens are allowed to roam a little bit (but the coyotes, raccoons and fox all like this too much)however they do not have access to 'natural' sources of grit and calcium. By supplementing their diet, I do not have egg eaters. Of course, some hens don't read my posts and they will develop a taste for eggs anyway.... But I think adding free choice calcium and granite grit for them would be good.

It's annoying when a hen (or hens) do this. But I have a few more thoughts to add, after moving two flocks together in the same coop. I've been observing what's going on. I suspect I caused the egg eating by confining them together, with limited food stations. It was enough for one flock, but two? The dominant hens who were already in the coop, were ensuring the newbies couldn't get to the food. The new hens would also try and escape, whenever I opened the door - to get to the food outside!

None of the dominant hens did this, as they were safe in the knowledge they had access to food, any time. The other hens (which outnumbered the dominant ones) weren't getting enough food. I suspect your lonely food station may not be getting accessed, by hens lower down in the pecking order. They will constantly be chased away, even if they get to peck a few times. They may be poking their head through to get to food outside - and when they realise they can't get out, eat the only thing they can access.

My hens have stopped eating their eggs, since I made a concerted effort to stand around the food scraps I bring up every morning, and prevent the dominant hens, chasing the new hens away. I also make sure to bring other foods in during the day too. So the lonely food station I keep grains in, isn't the only food available until the next morning. It might seem the hens should be content if you're moving the tractor around to new ground (ergo, more food) but if the dominant hens are constantly chasing the new ones away from prime pickings and the food station, their condition will drop and they'll get desperate enough to access what they can. Just some thoughts for you to consider.

If the egg eating only started when they moved to the tractor (as it suddenly happened when I moved two flocks together) then it's an indication the housing/food management is becoming an issue. This is not meant as a criticism, but hopefully something to help prevent the egg eating. It really is a pain when they do that.

We are 90% sure the chickens are getting enough calcium as we have not noticed any thin egg shells and the entire flock gets access to the laying pellets we use which has calcium as one of the ingredients.