With my testing,I stumble across a translation issue with Neuron. It seems that "the code" try to use the localized version of the states in ref to there indexes, and... It can not work ^^.
To avoid this, I've change this in Neuron.lua :
NEURON.STATEINDEX = { paged = "paged", stance = "stance", pet = "pet", alt = "alt", ctrl = "ctrl", shift = "shift", stealth = "stealth", reaction = "reaction", combat = "combat", group = "group", fishing = "fishing", vehicle = "vehicle", possess = "possess", override = "override", extrabar = "extrabar", prowl = "prowl", custom = "custom", target = "target", }
Then, translation and addon works flawlessly :)

You're absolutely right. Nice catch, being that I only use English I hadn't run into this error yet. I implemented this fix