You are welcome to provide images...
It sounds like a simple case of
reversion, where the selection/cultivar with non-standard foliage will produce foliage that has reverted to the species characteristics.
A very common example of this:
Picea glauca 'Conica' (Dwarf or Compact Alberta Spruce) is a very dense short needled selection of this species. Just about any plant that has been in the ground established for 5-10 years will throw a reversion stem. It is very obvious when you see it, and it needs to be pruned out because it rapidly wants to grow into the full sized species tree.
