So, i was trying to get sheathe stance to work for like hours. Until i finally figured that your transparency of the interfaces have to be 0. If there is only a little transparency (being able to see through ur interfaces) it will cancel out the sheathed effect.
More so the case that the transparency changes the colors that it's comparing the base to, leading to false positives and such. Certain backgrounds such as grey roads and dark objects can counteract this but you have to be in very specific places for this to work.