Check in your prod environment if there are any unmanaged layers of customization on that column, and see if the dependencies match dev.
I would also see if you can alter the PowerFx formula to remove the reference to Chapter, save, modify the length of the field, modify the formula column to re-add Chapter, save, publish table.
you may have to also do a temporary push to prod that just unlinks Chapter from the formula column, and another push to prod that relinks them with the higher field length.
It does look like a bug to me if it can’t be resolved with the above steps so you may have to contact Microsoft support.