Don't know if it's a lethal gene or not but many would pip and die, some would hatch but die a day or two later and others would be fine for a couple of weeks, they appeared to have 'failure to thrive' syndrome.
This was with both Valleys and Blue Scale crossed with Bobwhites.
Seeing how your chick isn't a true Bob x Valley cross, might be the reason it is thriving....old world genes mixed with new world genes...two seperate species, so, I would expect it to be a hybrid and sterile as well.
A&M Bob's are mixture of English Whites and Coturnix and for all practical purposes are Coturnix quail.
Wild populations of Bobwhites and Blue Scaled quail with a cross (hybrids) have been known to exist since 1890. It is usually a 'one and done' deal, as the hybrids are sterile.