I'm very sorry to be unable to assist you, as I have never used incubators. With the mass loss being over recommended though one would think this even unlikelier still an occurrence. It'd make more sense if it was under, but I've hatched chicks from eggs that were under recommended mass loss; it was no problem, the eggs didn't split. But these I let the hens hatch, only assisting if the chicks couldn't hatch unassisted, it wasn't an incubator job, but after hatching hundreds of chicks you get a feel for which eggs are not developing correctly.
However I do believe you are most likely dealing with a genetic trait here. I don't know of anything else that could cause an embryo to exceed its environment capacity, except disease, but that isn't too likely here I think. Breeding for rapid size gain could conceivably cause the embryo to exceed egg size, after all it works that way in mammals too when they've been bred for rapid size gain. They reach a stage where the embryo's excessive development threatens the integrity of its environment. I know comparing mammals and avians is technically incorrect but there are some parallels.
You're in the right forum, someone who knows something specific about this should come along and answer, but if they don't it's probably because they don't know. It's certainly a strange occurrence.
Are all the eggs from the same hen and tom? If you are unable to find information on this, repeating the breeding would possibly shed some light on the genetic theory. There's a lot of things that don't make sense until your breeding records are in good order, really invaluable stuff. If you bought the eggs though that's not going to help you too much, unless you contact the hatchery and ask if anyone else has reported this or if they know what it is.
All the best.
