Possible flawwith HovaBator design. Anyone else noticed this?

[eggbuster]

It may be uneven room temperature. I have two hovabators and am noticing a definite cold side on both of them. The eggs along one side of each, consistently hatch slower or fail to fully develop while the opposite side always hatches first. I am rotating the incubators daily to see if it makes a difference on the latest hatch.