It is very likely caused by the game. Could be that the accuracy is being calculated by other values so changing the accuracy itself has no effect and gets reset.
So there is no way to change accuracy now??
I've been using these options to circumvent accuracy.
Edit: Bonus Graze To Hit Percent
Edit: Bonus Miss To Graze Percent
Edit: Bonus Hit To Crit Percent
It does not give you the satisfaction of seeing the actual stat increase ingame, but it can give you as good a hit/crit chance as you want.