I have had all kinds of problems with touchID, just too unreliable. Like xiaomi phones that are getting popular, when you do 2+1 touch, touches just freeze/reset. So i just use TouchIndex or variables.
You could possible set TouchId to some unique vars, but when on xiamo touchID reset at 3 touches, 4 can be same as 1. Maybe you got some super good workaround, not sure about that.
So i encourage people not to use TouchID.