If you put a single point into Hewed Flesh or Unliving Energy, you aren’t able to remove it and ignore that section of the skill tree. A “broken path” error populates forcing you to commit a skill point there. 
this isnt a bug. it means if you remove a point from it you have points in a further path that wouldnt be reachable without that point. you need a set amount of points to reach the next group of nodes and without that point you cant reach it