I believe that large eggs like that put pressure on the nerves that lead to their legs which is what makes them temporarily unable to stand or walk. Enlarged internal organs can also have the same effect. It's not always Marek's as is often touted when chickens can't walk.All 11 of my girls are laying!!!
Daisy, the last hold out laid her first egg since the middle of September. In a way I would have been fine if she never laid another egg. I almost lost her last year to a huge double yolk egg getting stuck. It took 2 days for that thing to pass, and it must have been pressing on a nerve because one minute she was fine, the next she couldn't stand. I thought I was going to loose her to a neurological problem and was sure it was possibly mareks at first. Didn't think of a egg issue as she'd already laid that morning. Kept her isolated inside for 2 days trying to help her walk when the 2nd morning she popped out a monster egg, thought at first it was a triple yolk. After the egg passed she was able although shakily able to stand and it took a week for her to get back to herself. She laid 2 more normal eggs after that and was done. This first egg back of hers, is of course a big one, she lays the largest eggs of any of my hens but i'm going to keep a very close eye on her and pray no more double yolks. Of all the girls who I would be happy to be a non laying free loader its Daisy.