It looks like this works with the fingerprint set up before the screen protector is added. The catch here, I believe, is that the screen protector needs to hav

It looks like this works with the fingerprint set up before the screen protector is added. The catch here, I believe, is that the screen protector needs to have some sort of gel adhesive and it only unlocks if you've pressed a valid finger against the screen protector prior to using the invalid finger. Pressing the valid finger against the protector leaves an imprint in the gel, and this is what is read when it reads the invalid finger. I don't think that this is a bug in Samsung's code but rather a flaw in the technology that they chose to use.