When I went through the character generator the class abilities for Ranger and fighter "fighting style- Archer" doubles.  As far as I am aware, this should not be the case.

A main point of fighting styles would have to be "You can’t take a Fighting Style option more than once, even if something in the game lets you choose again." However, when you multiclass from a class that allows a fighting style option into another class that also allows a fighting style option, ie. college of swords bard into paladin, the options allow you to choose the same fighting style and even displays a stacking effect. In the same example of the bard/paladin, a level 3 CoS bard can pick dueling allowing a +2 to damage rolls and at paladin level 2 the same character is given the option to pick the dueling fighting style again for what is shown as an additional +2 damage. By the basic rules this shouldn't be possible.