Some units that are created from standard units like cartoon beetles and priests give the green blocks in game when you look at the unit to train. I’ve used raw code of the icon, copied and pasted, but it doesn’t keep the green icon from appearing instead of the actual unit.
Priest and All the carrion beetles are some that I’ve noticed with this bug. This is a big issue as you could spend time customizing a unit only to not be able to apply the correct icon.